7 Oracle Configuration Best Practices< /title> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <meta http-equiv="Content-Language" content="EN"> <m eta http-equiv="Content-Style-Type" content="text/css"> <meta http-equiv="Content-Script-Type" content="text/javascript"> <meta name= "robots" content="all" scheme="http://www.robotstxt.org/"> <meta name="doctitle" content="Oracle® High Availability Architecture and Best Practices 10g Release 1 (10.1)"> <meta name="partno" content="B10726-01"> <meta name="docid" content="MAXAV"> <link rel="Sta rt" href="../../index.htm" title="Home" type="text/html"> <link rel="Copyright" href="../../dcommon/html/cpyr.htm" title="Copyright" type="text/html"> <link rel="Stylesheet" href="../../dcommon/css/doccd.css" title="Default" type="text/css"> <link rel="Contents" hre f="toc.htm" title="Contents" type="text/html"> <link rel="Index" href="index.htm" title="Index" type="text/html"> <link rel="Prev" hr ef="sysnet.htm" title="Previous" type="text/html"> <link rel="Next" href="partpage4.htm" title="Next" type="text/html"> <link rel="al ternate" href="../b10726.pdf" title="PDF version" type="application/pdf"> </head> <body> <div class="header"> <p><a name="top" id="to p" href="#BEGIN">Skip Headers</a></p> <table summary="" cellspacing="0" cellpadding="0" width="100%"> <tr> <td align="left" valign="t op"><font color="#330099" face="Helvetica, Arial, sans-serif"><strong>Oracle® High Availability Architecture and Best Practices<b r> 10<i>g</i> Release 1 (10.1)</strong><br> Part Number B10726-01</font></td> <td valign="bottom" align="right"> <table summary="" c ellspacing="0" cellpadding="0" width="270"> <tr> <td align="center" valign="top"><a href="../../index.htm"><img src="../../dcommon/gi fs/prodicon.gif" alt="Go to Documentation Home" border="0"><br> <font size="-2">Home</font></a></td> <td align="center" valign="top"> <a href="../../nav/portal_3.htm"><img src="../../dcommon/gifs/bookicon.gif" alt="Go to Book List" border="0"><br> <font size="-2">Boo k List</font></a></td> <td align="center" valign="top"><a href="toc.htm"><img src="../../dcommon/gifs/conticon.gif" alt="Go to Table of Contents" border="0"><br> <font size="-2">Contents</font></a></td> <td align="center" valign="top"><a href="index.htm"><img src=". ./../dcommon/gifs/indxicon.gif" alt="Go to Index" border="0"><br> <font size="-2">Index</font></a></td> <td align="center" valign="to p"><a href="../../mix$101/b12039/toc.htm"><img src="../../dcommon/gifs/mix.gif" alt="Go to Master Index" border="0"><br> <font size=" -2">Master Index</font></a></td> <td align="center" valign="top"><a href="../../dcommon/html/feedback.htm"><img src="../../dcomm on/gifs/feedback.gif" alt="Go to Feedback page" border="0"><br> <font size="-2">Feedback</font></a></td></tr></table></td></tr></tabl e> <hr> <table summary="layout table" cellspacing="0" cellpadding="0" width="100%"> <tr> <td align="left" valign="top"> <table summar y="layout table" cellspacing="0" cellpadding="0" align="left" width="90"> <tr> <td align="center" valign="top"><a href="sysnet.htm">< img src="../../dcommon/gifs/larrow.gif" alt="Go to previous page" border="0"><br> <font size="-2">Previous</font></a></td> <td align= "center" valign="top"><a href="partpage4.htm"><img src="../../dcommon/gifs/rarrow.gif" alt="Go to next page" border="0"><br> <font si ze="-2">Next</font></a></td></tr></table></td> <td align="right" valign="top"><a href="../b10726.pdf"><font size="-2">View PDF</font> </a></td></tr></table> <a name="BEGIN"></a></div> <div class="IND"> <a name="1006182"></a>  <h1 class="Title"><font face="Arial, Helvetica, sans-serif" color="#330099">7<br> <a name="MAXAV008"></a><a name="MAXAV008">Orac le Configuration Best Practices</a></font></h1>  <a name="1011738"></a> <p class="BP">This chapter describes Oracle configuration best practices. It includes the following sections:</p> <ul class="LB1"> <li class="LB1" type="disc"><a name="1010825" ></a><a href="configbp.htm#1010798">Configuration Best Practices for the Database</a></li> <li class="LB1" type="disc"><a name="10158 28"></a><a href="configbp.htm#1012434">Configuration Best Practices for Real Application Clusters</a></li> <li class="LB1" type="disc "><a name="1015832"></a><a href="configbp.htm#1007027">Configuration Best Practices for Data Guard</a></li> <li class="LB1" type="dis c"><a name="1015833"></a><a href="configbp.htm#1013204">Configuration Best Practices for MAA</a></li> <li class="LB1" type="disc"><a name="1015930"></a><a href="configbp.htm#1007375">Recommendations for Backup and Recovery</a></li> <li class="LB1" type="disc"><a nam e="1010714"></a><a href="configbp.htm#1010806">Recommendations for Fast Application Failover</a> <p><a name="1016309"></a></p> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout ta ble to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1016312">< /a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1016313"></a> <p class="NB"><a hr ef="appconfig.htm#620714">Appendix B, "Database SPFILE and Oracle Net Configuration File Samples"</a> for a complete example of database parameter settings</p></td></tr></table></div></li></ul> <a name="1010798"></a>  <h2 class="H1"><font face="Arial, Helvetica, sans-serif" color="#330099">Configuration Best Practices for the Database</font></h2>  <a name ="1006670"></a> <p class="BP">The practices that are recommended in this section affect the performance, availability, and MTTR of y our system. These practices apply to the single-instance database, RAC-only, Data Guard-only, and Maximum Availability architectures described in <a href="architectures.htm#1004903">Chapter 4, "High Availability Architectures"</a>. The recommendations in this s ection are identical for the primary and standby databases when Oracle Data Guard is used. Some of these practices may reduce perform ance, but they are necessary to reduce or avoid outages. The minimal performance impact is outweighed by the reduced risk of corrupti on or the performance improvement for recovery.</p> <a name="1015834"></a> <p class="BP">This section includes the following recomme ndations:</p> <dl class="LS"> <dt class="LSF"><a name="1015835"></a><a href="configbp.htm#1006878">Use Two Control Files</a></dt> <dt class="LSF"><a name="1015843"></a><a href="configbp.htm#1006908">Set CONTROL_FILE_RECORD_KEEP_TIME Large Enough</a></dt> <dt class=" LSF"><a name="1015847"></a><a href="configbp.htm#1006921">Configure the Size of Redo Log Files and Groups Appropriately</a></dt> <dt class="LSF"><a name="1015851"></a><a href="configbp.htm#1006950">Multiplex Online Redo Log Files</a></dt> <dt class="LSF"><a name="10 15855"></a><a href="configbp.htm#1006954">Enable ARCHIVELOG Mode</a></dt> <dt class="LSF"><a name="1015859"></a><a href="configbp.htm #1006963">Enable Block Checksums</a></dt> <dt class="LSF"><a name="1015863"></a><a href="configbp.htm#1006970">Enable Database Block Checking</a></dt> <dt class="LSF"><a name="1015867"></a><a href="configbp.htm#1006980">Log Checkpoints to the Alert Log</a></dt> <dt class="LSF"><a name="1015871"></a><a href="configbp.htm#1006984">Use Fast-Start Checkpointing to Control Instance Recovery Time</a></ dt> <dt class="LSF"><a name="1015875"></a><a href="configbp.htm#1006993">Capture Performance Statistics About Timing</a></dt> <dt cla ss="LSF"><a name="1015879"></a><a href="configbp.htm#1006997">Use Automatic Undo Management</a></dt> <dt class="LSF"><a name="1015883 "></a><a href="configbp.htm#1007006">Use Locally Managed Tablespaces</a></dt> <dt class="LSF"><a name="1015887"></a><a href="configbp .htm#1007010">Use Automatic Segment Space Management</a></dt> <dt class="LSF"><a name="1015891"></a><a href="configbp.htm#1007014">Us e Temporary Tablespaces and Specify a Default Temporary Tablespace</a></dt> <dt class="LSF"><a name="1015895"></a><a href="configbp.h tm#1007019">Use Resumable Space Allocation</a></dt> <dt class="LSF"><a name="1015899"></a><a href="configbp.htm#1013620">Use a Flash Recovery Area</a></dt> <dt class="LSF"><a name="1015907"></a><a href="configbp.htm#1014382">Enable Flashback Database</a></dt> <dt cl ass="LSF"><a name="1015911"></a><a href="configbp.htm#1014384">Set Up and Follow Security Best Practices</a></dt> <dt class="LSF"><a name="1015915"></a><a href="configbp.htm#1014386">Use the Database Resource Manager</a></dt> <dt class="LSF"><a name="1016317"></a><a href="configbp.htm#1016346">Use a Server Parameter File</a></dt></dl> <a name="1006878"></a>  <h3 class="H2"> <font face="Arial, Helvetica, sans-serif" color="#330099">Use Two Control Files</font></h3>  <a name="1006879"></a> <p class="BP">Maintain two copies of the control file. If a single control file is damaged, then any Oracle instance fails when it atte mpts to access the damaged or missing control file. If another copy of the current control file is available, then an instance can be easily restarted after copying the good control file to the location of the bad control file. Database recovery is unnecessary.</p> <a name="1006889"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class=" NoteAlso"><a name="1006882"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="10068 88"></a> <p class="NB"><em class="Italic"><a class="olinkSRC ADMIN" href="../../server$101/b10739/toc.htm">Oracle Database Administr ator's Guide</a></em></p></td></tr></table></div> <a name="1006908"></a>  <h3 class="H2"><font face="Arial, He lvetica, sans-serif" color="#330099">Set CONTROL_FILE_RECORD_KEEP_TIME Large Enough</font></h3>  <a name="1006909"></a> <p class="BP">Set the <code>CONTROL_FILE_RECORD_KEEP_TIME</code> initialization parameter to a value that enables all on-disk backu p information to be retained in the control file. Allocate 200 MB for each control file. <code>CONTROL_FILE_RECORD_KEEP_TIME</code> s pecifies the number of days that records are kept within the control file before becoming a candidate for reuse. Set the <code>CONTRO L_FILE_RECORD_KEEP_TIME</code> value to slightly longer than the oldest backup file that you intend to keep on disk, as determined by the size of the flash recovery area. For example, if the flash recovery area is sized to maintain two full backups that are taken ev ery 7 days, as well as daily incremental backups and archived redo log files, then set <code>CONTROL_FILE_RECORD_KEEP_TIME</code> to a value like 21 or 30. Records older than this will be reused. However, the backup metadata will still be available in the RMAN recov ery catalog.</p> <a name="1006919"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspac ing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class="NoteA lso"> <td class="NoteAlso"><a name="1006912"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></fon t> <a name="1006918"></a> <p class="NB"><em class="Italic"><a class="olinkSRC BRADV" href="../../server$101/b10734/toc.htm">Oracle D atabase Backup and Recovery Advanced User's Guide</a></em></p></td></tr></table></div> <a name="1006921"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Configure the Size of Redo Log Files and Groups Appropriate ly</font></h3>  <a name="1015645"></a> <p class="BP">All online redo log files should be the same size and configured to switch approximately once an hour during normal activity. They should switch no more frequently than every 20 minutes during peak activity.</p> <a name="1015648"></a> <p class="BP">There should be a minimum of four online log groups to prevent <code>LGWR</code> from waiting for a group to be available following a log switch. A group may be unavailable because a checkpoint has not yet complete d or the group has not yet been archived.</p> <a name="1006948"></a> <div align="center"> <table class="NoteAlso" border="0" width=" 80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to for mat a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1006926"></a><font face="Arial, Helvetica, sans-serif"><strong class ="NH">See Also:</strong></font> <a name="1006927"></a> <ul class="NL"> <li class="NL" type="disc"><a name="1006934"></a><em class="I talic"><a class="olinkSRC ADMIN" href="../../server$101/b10739/toc.htm">Oracle Database Administrator's Guide</a></em></li> <li class ="NL" type="disc"><a name="1006940"></a><em class="Italic"><a class="olinkSRC SBYDB" href="../../server$101/b10823/toc.htm">Oracle Da ta Guard Concepts and Administration</a></em></li> <li class="NL" type="disc"><a name="1006947"></a><a href="configbp.htm#1007027">"C onfiguration Best Practices for Data Guard"</a><a href="configbp.htm#1007027"></a></li></ul></td></tr></table></div> <a name="1006950 "></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Multiplex Online Redo Log Fil es</font></h3>  <a name="1006951"></a> <p class="BP">Use Oracle log multiplexing to create multiple redo log members i n each redo group. This protects against a failure involving the redo log, such as a disk corruption that exists on both sides of the disk mirror for one of the members, or a user error that accidentally removes a member. If at least one redo log member is available , then the instance can continue to function.</p> <a name="1007698"></a> <div align="center"> <table class="NoteAlso" border="0" wid th="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1007701"></a><font face="Arial, Helvetica, sans-serif"><strong c lass="NH">See Also:</strong></font> <a name="1007710"></a> <p class="NB"><em class="Italic"><a class="olinkSRC ADMIN" href="../../se rver$101/b10739/toc.htm">Oracle Database Administrator's Guide</a></em></p></td></tr></table></div> <a name="1006954"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Enable ARCHIVELOG Mode</font></h3>  <a name="1006955"></a> <p class="BP"><code>ARCHIVELOG</code> mode enables the database to be backed up while it is online and is necessary to recover the database to a point in time later than what has already been restored.</p> <a name="1012406"></a> <p class ="BP">Architectures that include Oracle Data Guard require that the production database run in <code>ARCHIVELOG</code> mode before a standby database is instantiated. <code>ARCHIVELOG</code> mode is required to maintain a standby database.</p> <a name="1012405"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a la yout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="100 7728"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1007735"></a> <p class="NB "><em class="Italic"><a class="olinkSRC ADMIN" href="../../server$101/b10739/toc.htm">Oracle Database Administrator's Guide</a></em> for more information about using automatic archiving</p></td></tr></table></div> <a name="1006963"></a>  <h3 c lass="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Enable Block Checksums</font></h3>  <a name="100696 4"></a> <p class="BP">By default, Oracle always tests the data blocks that it reads from disk. Enabling data and log block checksums by setting <code>DB_BLOCK_CHECKSUM</code> to <code>TRUE</code> enables Oracle to detect other types of corruption caused by underlyi ng disks, storage systems, or I/O systems. Before a data block is written to disk, a checksum is computed and stored in the block. Wh en the block is subsequently read from disk, the checksum is computed again and compared with the stored checksum. Any difference is treated as a media error and an ORA-1578 error is signaled. Block checksums are always maintained for the <code>SYSTEM</code> tablesp ace.</p> <a name="1006965"></a> <p class="BP">In addition to enabling data block checksums, Oracle also calculates a checksum for ev ery redo log block before writing it to the current log. Redo record corruptions are found as soon as the log is archived. Without th is option, a corruption in a redo log can go unnoticed until the log is applied to a standby database or until a backup is restored a nd rolled forward through the log containing the corrupt log block.</p> <a name="1006966"></a> <p class="BP">RMAN also calculates ch ecksums when taking backups to ensure that all blocks being backed up are validated.</p> <a name="1006967"></a> <p class="BP">Turnin g on this feature typically has minimal overhead. Measure the performance impact with your workload on a test system and ensure that the performance impact is acceptable before introducing this feature on an active database.</p> <a name="1007804"></a> <div align="c enter"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to f ormat a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1007808"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1007815"></a> <p class="NB"><em class="It alic"><a class="olinkSRC ADMIN" href="../../server$101/b10739/toc.htm">Oracle Database Administrator's Guide</a></em></p></td></tr></ table></div> <a name="1006970"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099"> Enable Database Block Checking</font></h3>  <a name="1006971"></a> <p class="BP">Enable database block checking by set ting <code>DB_BLOCK_CHECKING</code> to <code>TRUE</code>. When block checking is enabled, whenever a block is modified, Oracle verifi es that the block is self-consistent. If it is inconsistent, then the block is marked corrupt, an ORA-1578 error is returned, and a t race file is created containing details of the problem. Without block checking enabled, corruptions can go undetected until the block is accessed again. Block checking for the <code>SYSTEM</code> tablespace is always enabled.</p> <a name="1006972"></a> <p class="BP ">Block checking can often prevent memory and data corruption. Turning on this feature typically causes an additional 1 percent to 10 percent overhead, depending on workload. Measure the performance impact on a test system using your workload and ensure that it is a cceptable before introducing this feature on an active database.</p> <a name="1006973"></a> <p class="BP">To ensure that blocks are not corrupted externally to Oracle, use one of the following:</p> <ul class="LB1"> <li class="LB1" type="disc"><a name="1006974"></a> RMAN <code>BACKUP</code> command with the <code>VALIDATE</code> option</li> <li class="LB1" type="disc"><a name="1007859"></a><code>D BVERIFY</code> utility</li> <li class="LB1" type="disc"><a name="1007860"></a><code>ANALYZE TABLE</code> <em><code>tablename</code></ em> <code>VALIDATE STRUCTURE CASCADE</code> SQL statement <p><a name="1007871"></a></p> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1007863"></a><font face="Arial, Helvetica, sans-s erif"><strong class="NH">See Also:</strong></font> <a name="1007870"></a> <p class="NB"><em class="Italic"><a class="olinkSRC ADMIN" href="../../server$101/b10739/toc.htm">Oracle Database Administrator's Guide</a></em></p></td></tr></table></div></li></ul> <a name= "1006980"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Log Checkpoints to th e Alert Log</font></h3>  <a name="1006981"></a> <p class="BP">Checkpoint activity should be logged to the alert log by setting <code>LOG_CHECKPOINT_TO_ALERT</code> to <code>TRUE</code>. Monitor checkpoint activity to ensure that a current checkpoint c ompletes before the next checkpoint starts.</p> <a name="1006982"></a> <div align="center"> <table class="NoteAlso" border="0" width ="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to f ormat a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1007881"></a><font face="Arial, Helvetica, sans-serif"><strong cla ss="NH">See Also:</strong></font> <a name="1007882"></a> <p class="NB"><em class="Italic"><a class="olinkSRC REFRN" href="../../serv er$101/b10755/toc.htm">Oracle Database Reference</a></em></p></td></tr></table></div> <a name="1006984"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Use Fast-Start Checkpointing to Control Instance Recovery Ti me</font></h3>  <a name="1014783"></a> <p class="BP">Fast-start checkpointing refers to the periodic writes by the dat abase writer (<code>DBW</code><em class="Italic">n</em>) processes. <code>DBW</code><em><code>n</code></em> processes write changed d ata blocks from the Oracle buffer cache to disk and advance the thread checkpoint. With fast-start checkpointing, the checkpoint cont inually advances so that recovery time from instance or node failure occurs predictably.</p> <a name="1014789"></a> <p class="BP">Or acle Database 10<em class="Italic">g</em> supports automatic checkpoint tuning which takes advantage of periods of low I/O usage to a dvance checkpoints and therefore improve availability. Automatic checkpoint tuning is in effect if the <code>FAST_START_MTTR_TARGET</ code> database initialization parameter is unset. Observe the following recommendations to take advantage of automatic checkpoint tun ing:</p> <ul class="LB1"> <li class="LB1" type="disc"><a name="1014795"></a>If it is necessary to control the time to recover from an instance or node failure, then set <code>FAST_START_MTTR_TARGET</code> to the desired MTTR in seconds.</li> <li class="LB1" type="di sc"><a name="1014798"></a>If targeting a specific MTTR is unnecessary, then leave <code>FAST_START_MTTR_TARGET</code> unset to enable automatic checkpoint tuning.</li> <li class="LB1" type="disc"><a name="1014801"></a>Fast-start checkpointing can be disabled by sett ing <code>FAST_START_MTTR_TARGET=0</code>. Disable fast-start checkpointing only when system I/O capacity is insufficient with fast-s tart checkpointing enabled and achieving a target MTTR is not important.</li></ul> <a name="1014806"></a> <p class="BP">Enabling fas t-start checkpointing increases the average number of writes per transaction that <code>DBW</code><em><code>n</code></em> issues for a given workload (when compared with disabling fast-start checkpointing). However, if the system is not already near or at its maximu m I/O capacity, then fast-start checkpointing has a negligible impact on performance. The percentage of additional <code>DBW</code><e m><code>n</code></em> writes with very aggressive fast-start checkpointing depends on many factors, including the workload, I/O speed and capacity, CPU speed and capacity, and the performance of previous recoveries.</p> <a name="1016328"></a> <p class="BP">Monitor the <code>V$MTTR_TARGET_ADVICE</code> view for advisory information and an estimate of the number of additional I/O operations that w ould occur under different <code>FAST_START_MTTR_TARGET</code> values. You should also test various <code>FAST_START_MTTR_TARGET</cod e> settings (such as <code>0</code>, <code>1</code>, <code>90</code>, <code>180</code>, <code>270</code>, <code>3600</code>, and unse t) under load to determine the runtime impact (for example, the amount of increased <code>DBW</code><em><code>n</code></em> write act ivity) on a particular system and the instance recovery time achieved with that setting.</p> <a name="1014818"></a> <p class="BP">If <code>FAST_START_MTTR_TARGET</code> is set to a low value, then fast-start checkpointing is more aggressive, and the average number of writes per transaction that <code>DBW</code><em><code>n</code></em> issues is higher in order to keep the thread checkpoint suffic iently advanced to meet the requested MTTR. Conversely, if <code>FAST_START_MTTR_TARGET</code> is set to a high value, or if automati c checkpoint tuning is in effect (that is, <code>FAST_START_MTTR_TARGET</code> is unset), then fast-start checkpointing in less aggre ssive, and the average number of writes per transaction that <code>DBW</code><em><code>n</code></em> issues is lower.</p> <a name="10 14826"></a> <p class="BP">Fast-start checkpointing can be explicitly disabled by setting <code>FAST_START_MTTR_TARGET=0</code>. Disa bling fast-start checkpointing leads to the fewest average number of writes per transaction for <code>DBW</code><em><code>n</code></e m> for a specific workload and configuration, but also results in the highest MTTR.</p> <a name="1014831"></a> <p class="BP">When yo u enable fast-start checkpointing, remove or disable (set to <code>0</code>) the following initialization parameters: <code>LOG_CHECK POINT_INTERVAL</code>, <code>LOG_CHECKPOINT_TIMEOUT</code>, <code>FAST_START_IO_TARGET</code>.</p> <a name="1007910"></a> <div align ="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table t o format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1007913"></a><f ont face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1007915"></a> <p class="NB"><em class= "Italic"><a class="olinkSRC PFGRF" href="../../server$101/b10752/toc.htm">Oracle Database Performance Tuning Guide</a></em></p></td>< /tr></table></div> <a name="1006993"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#33 0099">Capture Performance Statistics About Timing</font></h3>  <a name="1006994"></a> <p class="BP">Set the <code>TIME D_STATISTICS</code> initialization parameter to <code>TRUE</code> to capture Oracle event timing data. This parameter is set to <code >TRUE</code> by default if the <code>STATISTICS_LEVEL</code> database parameter is set to its default value of <code>TYPICAL</code>. Effective data collection and analysis is essential for identifying and correcting system performance problems. Oracle provides sever al tools that allow a performance engineer to gather information about instance and database performance. Setting <code>TIMED_STATIST ICS</code> to <code>TRUE</code> is essential to effectively using the Oracle tools.</p> <a name="1007939"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1007942"></a><font face="A rial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1007950"></a> <ul class="NL"> <li class="NL" type ="disc"><a name="1016330"></a><em class="Italic"><a class="olinkSRC PFGRF" href="../../server$101/b10752/toc.htm">Oracle Database Per formance Tuning Guide</a></em> for information about Oracle's performance methodology and new performance tuning features</li> <li cl ass="NL" type="disc"><a name="1016331"></a><em class="Italic"><a class="olinkSRC OEMCN" href="../../em$101/b12016/toc.htm">Oracle Ent erprise Manager Concepts</a></em> for information about monitoring and diagnostic tools available with Oracle Enterprise Manage<em cl ass="Italic">r</em></li> <li class="NL" type="disc"><a name="1016332"></a><em class="Italic"><a class="olinkSRC ARPLS" href="../../ap pdev$101/b10802/toc.htm">PL/SQL Packages and Types Reference</a></em> for information about the <code>DBMS_ADVISOR</code>, <code>DBMS _SQLTUNE</code>, and <code>DBMS_WORKLOAD_REPOSITORY</code> PL/SQL packages</li></ul></td></tr></table></div> <a name="1006997"></a> < !--TOC=h2-"1006997"--> <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Use Automatic Undo Management</font>< /h3>  <a name="1006998"></a> <p class="BP">With automatic undo management, the Oracle server effectively and efficient ly manages undo space, leading to lower administrative complexity and cost. When Oracle internally manages undo segments, undo block and consistent read contention are eliminated because the size and number of undo segments are automatically adjusted to meet the cur rent workload requirement.</p> <a name="1006999"></a> <p class="BP">To use automatic undo management, set the following parameters:< /p> <ul class="LB1"> <li class="LB1" type="disc"><a name="1007000"></a><code>UNDO_MANAGEMENT = AUTO</code></li> <li class="LB1" type= "disc"><a name="1007001"></a><code>UNDO_RETENTION</code> is the desired time in seconds to retain undo data. It must be the same on a ll instances.</li> <li class="LB1" type="disc"><a name="1007002"></a><code>UNDO_TABLESPACE</code> should specify a unique undo tables pace for each instance.</li></ul> <a name="1015756"></a> <p class="BP">Advanced object recovery features, such as Flashback Query, F lashback Version Query, Flashback Transaction Query, and Flashback Table, require automatic undo management. These features depend on the <code>UNDO_RETENTION</code> setting. Retention is specified in units of seconds. By default, Oracle automatically tunes undo ret ention by collecting database use statistics and estimating undo capacity needs. You can affect this automatic tuning by setting the <code>UNDO_RETENTION</code> initialization parameter. The default value of <code>UNDO_RETENTION</code> is <code>900</code>. You do no t need to set this parameter if you want Oracle to tune undo retention. The <code>UNDO_RETENTION</code> value can be changed dynamica lly at any time by using the <code>ALTER SYSTEM</code> statement.</p> <a name="1015957"></a> <p class="BP">Setting <code>UNDO_RETENT ION</code> does not guarantee that undo data will be retained for the specified period of time. If undo data is needed for transactio ns, then the <code>UNDO_RETENTION</code> period is reduced so that transactions can receive the necessary undo data.</p> <a name="101 5758"></a> <p class="BP">You can guarantee that unexpired undo data is not overwritten even if it means that future operations that need to generate undo data will fail. This is done by specifying the <code>RETENTION GUARANTEE</code> clause for the undo tablespace when it is created by either the <code>CREATE DATABASE</code> or <code>CREATE UNDO TABLESPACE</code> statement. Alternatively, you ca n later specify this clause in an <code>ALTER TABLESPACE</code> statement.</p> <a name="1015760"></a> <p class="BP">With the retenti on guarantee option, the undo guarantee is preserved even if there is need for DML activity. (DDL statements are still allowed.) If t he tablespace is configured with less space than the transaction throughput requires, the following four things will occur in this se quence:</p> <ol class="LN1" type="1"> <li class="LN1" type="1" value="1"><a name="1015761"></a>If you have an autoextensible file, th en it will automatically grow to accommodate the retained undo data.</li> <li class="LN1" type="1" value="2"><a name="1015762"></a>A warning alert is issued at 85 percent full.</li> <li class="LN1" type="1" value="3"><a name="1015763"></a>A critical alert is issued at 97 percent full.</li> <li class="LN1" type="1" value="4"><a name="1015764"></a>Transactions receive an out-of-space error. <p><a name="1007976"></a></p> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class=" NoteAlso"><a name="1007980"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="10079 82"></a> <p class="NB"><em class="Italic"><a class="olinkSRC ADMIN" href="../../server$101/b10739/toc.htm">Oracle Database Administr ator's Guide</a></em> for more information about the <code>UNDO_RETENTION</code> setting and the size of the undo tablespace</p></td> </tr></table></div></li></ol> <a name="1007006"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Use Locally Managed Tablespaces</font></h3>  <a name="1007007"></a> <p class="BP">Locally managed tab lespaces perform better than dictionary-managed tablespaces, are easier to manage, and eliminate space fragmentation concerns. Locall y managed tablespaces use bitmaps stored in the datafile headers and, unlike dictionary managed tablespaces, do not contend for centr ally managed resources for space allocations and de-allocations.</p> <a name="1007995"></a> <div align="center"> <table class="NoteA lso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This i s a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1007998"></a><font face="Arial, Helvetica, sa ns-serif"><strong class="NH">See Also:</strong></font> <a name="1007999"></a> <p class="NB"><em class="Italic"><a class="olinkSRC AD MIN" href="../../server$101/b10739/toc.htm">Oracle Database Administrator's Guide</a></em></p></td></tr></table></div> <a name="10070 10"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Use Automatic Segment Space Management</font></h3>  <a name="1007011"></a> <p class="BP">Automatic segment space management simplifies space admi nistration tasks, thus reducing the chance of human error. An added benefit is the elimination of performance tuning related to space management. It facilitates management of free space within objects such as tables or indexes, improves space utilization, and provid es significantly better performance and scalability with simplified administration. The automatic segment space management feature is available only with permanent locally managed tablespaces.</p> <a name="1008007"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a l ayout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1008088"></a><font face="Arial, Helvetica, sans-se rif"><strong class="NH">See Also:</strong></font> <a name="1008094"></a> <p class="NB"><em class="Italic"><a class="olinkSRC ADMIN" href="../../server$101/b10739/toc.htm">Oracle Database Administrator's Guide</a></em></p></td></tr></table></div> <a name="1007014">< /a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Use Temporary Tablespaces and Sp ecify a Default Temporary Tablespace</font></h3>  <a name="1007015"></a> <p class="BP">Temporary tablespaces improve t he concurrency of multiple sort operations, reduce sort operation overhead, and avoid data dictionary space management operations alt ogether. This is a more efficient way of handling temporary segments, from the perspective of both system resource usage and database performance.</p> <a name="1007016"></a> <p class="BP">A default temporary tablespace should be specified for the entire database to prevent accidental exclusion of the temporary tablespace clause. This can be done at database creation time by using the <code>DEFAU LT TEMPORARY TABLESPACE</code> clause of the <code>CREATE DATABASE</code> statement or after database creation by the <code>ALTER DAT ABASE</code> statement. Using the default temporary tablespace ensures that all disk sorting occurs in a temporary tablespace and tha t other tablespaces are not mistakenly used for sorting.</p> <a name="1008020"></a> <div align="center"> <table class="NoteAlso" bor der="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layo ut table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1008024"></a><font face="Arial, Helvetica, sans-serif "><strong class="NH">See Also:</strong></font> <a name="1008030"></a> <p class="NB"><em class="Italic"><a class="olinkSRC ADMIN" hre f="../../server$101/b10739/toc.htm">Oracle Database Administrator's Guide</a></em></p></td></tr></table></div> <a name="1007019"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Use Resumable Space Allocation</fon t></h3>  <a name="1007020"></a> <p class="BP">Resumable space allocation provides a way to suspend and later resume da tabase operations if there are space allocation failures. The affected operation is suspended instead of the database returning an er ror. No processes need to be restarted. When the space problem is resolved, the suspended operation is automatically resumed.</p> <a name="1016345"></a> <p class="BP">Set the <code>RESUMABLE_TIMEOUT</code> initialization parameter to the number of seconds of the re try time.</p> <a name="1008060"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing ="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso "> <td class="NoteAlso"><a name="1008064"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1008070"></a> <p class="NB"><em class="Italic"><a class="olinkSRC ADMIN" href="../../server$101/b10739/toc.htm">Oracle Data base Administrator's Guide</a></em></p></td></tr></table></div> <a name="1013620"></a>  <h3 class="H2"><font f ace="Arial, Helvetica, sans-serif" color="#330099">Use a Flash Recovery Area</font></h3>  <a name="1014309"></a> <p cl ass="BP">The flash recovery area is an Oracle-managed directory, file system, or automatic storage management disk group that provide s a centralized disk location for backup and recovery files. The flash recovery area is defined by setting the following database ini tialization parameters:</p> <ul class="LB1"> <li class="LB1" type="disc"><a name="1014312"></a><code>DB_RECOVERY_FILE_DEST</code>: De fault location for the flash recovery area</li> <li class="LB1" type="disc"><a name="1014314"></a><code>DB_RECOVERY_FILE_DEST_SIZE</c ode>: Specifies (in bytes) the hard limit on the total space to be used by target database recovery files created in the recovery are a location</li></ul> <a name="1014318"></a> <p class="BP">The bigger the flash recovery area, the more beneficial it becomes. The mi nimum recommended disk limit is the sum of the database size, the size of incremental backups, the size of all archived redo logs tha t have not been copied to tape, and the size of the flashback logs.</p> <a name="1014361"></a> <div align="center"> <table class="No teAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="Thi s is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1014364"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1014366"></a> <p class="NB"><em class="Italic"><a class="olinkSRC BRADV" href="../../server$101/b10734/toc.htm">Oracle Database Backup and Recovery Advanced User's Guide</a></em> and <em class="Ital ic"><a class="olinkSRC BRBSC" href="../../server$101/b10735/toc.htm">Oracle Database Backup and Recovery Basics</a></em> for detailed information about sizing the flash recovery area and setting the retention period</p></td></tr></table></div> <a name="1014382"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Enable Flashback Database</font></h 3>  <a name="1015682"></a> <p class="BP">Flashback Database is a revolutionary recovery feature that operates on only the changed data, thereby making the time to correct an error equal to the time to cause the error without recovery time being a func tion of the database size. You can flash back a database from both RMAN and SQL*Plus with a single command instead of a complex proce dure. Flashback Database is similar to conventional point-in-time recovery in its effects, enabling you to return a database to its s tate at a time in the recent past. However, Flashback Database is much faster than point-in-time recovery, because it does not requir e restoring datafiles from backup or extensive application of redo data.</p> <a name="1014393"></a> <p class="BP">To enable Flashbac k Database, set up a flash recovery area, and set a flashback retention target (<code>DB_FLASHBACK_RETENTION_TARGET</code> initializa tion parameter), to specify how far back into the past in minutes you want to be able to restore your database using Flashback Databa se. To enable Flashback Database, execute the <code>ALTER DATABASE FLASHBACK ON</code> statement. It is important to note that the fl ashback retention target is a target, not an absolute guarantee that Flashback Database will be available. If your flash recovery are a is not large enough to hold required files such as archived redo logs and other backups, then flashback logs may be deleted to make room in the flash recovery area for these required files. To determine how far you can flash back at any one time, query the <code>V $FLASHBACK_DATABASE_LOG</code> view. If you have a standby database, then set <code>FLASHBACK_RETENTION_TIME</code> to be the same fo r both primary and standby databases.</p> <a name="1014468"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1014471"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH ">See Also:</strong></font> <a name="1014472"></a> <p class="NB"><em class="Italic"><a class="olinkSRC BRADV" href="../../server$101 /b10734/toc.htm">Oracle Database Backup and Recovery Advanced User's Guide</a></em></p></td></tr></table></div> <a name="1014384"></a >  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Set Up and Follow Security Best Pr actices</font></h3>  <a name="1014500"></a> <p class="BP">The biggest threat to corporate data comes from employees an d contractors with internal access to networks and facilities. Corporate data is one of a company's most valuable assets that can be at grave risk if placed on a system or database that does not have proper security measures in place. A well-defined security policy can help protect your systems from unwanted access and protect sensitive corporate information from sabotage. Proper data protection reduces the chance of outages due to security breeches.</p> <a name="1014539"></a> <p class="BP">In addition to the "High Availabili ty" section in Chapter 9, "Oracle Security Products and Features", the <em class="Italic">Oracle Security Overview</em> manual is a h igh-level guide to technical security solutions for the data security challenge. Consult Part II, "Technical Solutions to Security Ri sks" of the <em class="Italic">Oracle Security Overview</em> for an overview of techniques for implementing security best practices. For a much more detailed view of security policies, checklists, guidelines, and features, see the <em class="Italic"><a class="olinkS RC DBSEG" href="../../network$101/b10773/toc.htm">Oracle Database Security Guide</a></em></p> <a name="1014385"></a> <div align="cen ter"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to for mat a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1014528"></a><font f ace="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1014529"></a> <p class="NB"><em class="Ital ic"><a class="olinkSRC SECOV" href="../../network$101/b10777/toc.htm">Oracle Security Overview</a></em> and <em class="Italic"><a cla ss="olinkSRC DBSEG" href="../../network$101/b10773/toc.htm">Oracle Database Security Guide</a></em></p></td></tr></table></div> <a na me="1014386"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Use the Database R esource Manager</font></h3>  <a name="1014543"></a> <p class="BP">The Database Resource Manager gives database adminis trators more control over resource management decisions, so that resource allocation can be aligned with the business objectives of a n enterprise. The Database Resource Manager provides the ability to prioritize work within the Oracle system. Availability of the dat abase encompasses both its functionality and performance. If the database is available but users are not getting the level of perform ance they need, then availability and service level objectives are not being met. Application performance, to a large extent, is affe cted by how resources are distributed among the applications that access the database. The main goal of the Database Resource Manager is to give the Oracle database server more control over resource management decisions, thus circumventing problems resulting from in efficient operating system management and operating system resource managers.</p> <a name="1014387"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1014564"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1014570"></a> <p class="NB"><em class="Italic"><a class ="olinkSRC ADMIN" href="../../server$101/b10739/toc.htm">Oracle Database Administrator's Guide</a></em></p></td></tr></table></div> < a name="1016346"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Use a Server P arameter File</font></h3>  <a name="1016347"></a> <p class="BP">The server parameter file (<code>SPFILE</code>) enable s a single, central parameter file to hold all of the database initialization parameters associated with all of the instances associa ted with a database. This provides a simple, persistent, and robust environment for managing database parameters.</p> <a name="101634 8"></a> <p class="BP">An <code>SPFILE</code> is required when using the Data Guard Broker.</p> <a name="1016349"></a> <div align="c enter"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to f ormat a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1016352"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1016353"></a> <ul class="NL"> <li class=" NL" type="disc"><a name="1016354"></a><em class="Italic"><a class="olinkSRC ADMIN" href="../../server$101/b10739/toc.htm">Oracle Data base Administrator's Guide</a></em></li> <li class="NL" type="disc"><a name="1016360"></a><em class="Italic"><a class="olinkSRC RACAD " href="../../rac$101/b10765/toc.htm">Oracle Real Application Clusters Administrator's Guide</a></em></li> <li class="NL" type="disc" ><a name="1016367"></a><em class="Italic"><a class="olinkSRC DGBKR" href="../../server$101/b10822/toc.htm">Oracle Data Guard Broker</ a></em></li> <li class="NL" type="disc"><a name="1017759"></a><a href="appconfig.htm#620714">Appendix B, "Database SPFILE and Or acle Net Configuration File Samples"</a></li></ul></td></tr></table></div> <a name="1012434"></a>  <h2 class=" H1"><font face="Arial, Helvetica, sans-serif" color="#330099">Configuration Best Practices for Real Application Clusters</font></h2>  <a name="1012441"></a> <p class="BP">The practices that are recommended in this section affect the performance, avail ability, and MTTR of your system. These practices build on the single instance database configuration best practices. The practices a re identical for the primary and standby databases if they are used with Data Guard in the MAA architecture. Some of these practices may reduce performance levels, but they are necessary to reduce or avoid outages. The minimal performance impact is outweighed by the reduced risk of corruption or the performance improvement for recovery.</p> <a name="1012533"></a> <p class="BP">The rest of this s ection includes the following topics:</p> <ul class="LB1"> <li class="LB1" type="disc"><a name="1012535"></a><a href="configbp.htm#10 16388">Register All Instances with Remote Listeners</a></li> <li class="LB1" type="disc"><a name="1016383"></a><a href="configbp.htm# 1016390">Do Not Set CLUSTER_INTERCONNECTS Unless Required for Scalability</a> <p><a name="1012582"></a></p> <div align="center"> <ta ble class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a not e" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1012587"></a><font face="Aria l, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1012604"></a> <p class="NB"><em class="Italic"><a cl ass="olinkSRC RACAD" href="../../rac$101/b10765/toc.htm">Oracle Real Application Clusters Administrator's Guide</a></em></p></td></tr ></table></div></li></ul> <a name="1016388"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" col or="#330099">Register All Instances with Remote Listeners</font></h3>  <a name="1016389"></a> <p class="BP">The listen ers should be cross-registered by using the <code>REMOTE_LISTENER</code> parameter so that all listeners know about all services and in which instances the services are running. The listeners should use server-side load balancing, which can be based on session count for connection. The listeners must be listening on the virtual IP addresses and on the cluster alias, when it is available. The list eners must <em class="Italic">not</em> listen on the hostname. Listening on the hostname will result in disconnected sessions when vi rtual IPs are relocated automatically back to their owning nodes.</p> <a name="1016400"></a> <div align="center"> <table class="Note Also" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1016403"></a><font face="Arial, Helvetica, s ans-serif"><strong class="NH"><strong class="Bold">See Also</strong>:</strong></font> <a name="1016404"></a> <ul class="NL"> <li cla ss="NL" type="disc"><a name="1016405"></a><em class="Italic"><a class="olinkSRC RACAD" href="../../rac$101/b10765/toc.htm">Oracle Rea l Application Clusters Administrator's Guide</a></em></li> <li class="NL" type="disc"><a name="1016411"></a><em class="Italic"><a cla ss="olinkSRC NETAG" href="../../network$101/b10775/toc.htm">Oracle Net Services Administrator's Guide</a></em></li></ul></td></tr></t able></div> <a name="1016390"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">D o Not Set CLUSTER_INTERCONNECTS Unless Required for Scalability</font></h3>  <a name="1016391"></a> <p class="BP">The <code>CLUSTER_INTERCONNECTS</code> initialization parameter should be set only if there is more than one cluster interconnect and the default cluster interconnect does not meet the throughput requirements of the RAC database. When <code>CLUSTER_INTERCONECTS</code> i s set to more than one network address, Oracle load-balances across the interfaces. However, there are no automatic failover capabili ties employed by Oracle, requiring that all interfaces be available for a properly functioning database environment.</p> <a name="101 6417"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="Th is is a layout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1016420"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1016421"></a> <p class="NB"><em class="Italic"><a class="olinkSRC RACAD" href="../../rac$101/b10765/toc.htm">Oracle Real Application Clusters Adminis trator's Guide</a></em></p></td></tr></table></div> <a name="1007027"></a>  <h2 class="H1"><font face="Arial, Helvetica, sans-serif" color="#330099">Configuration Best Practices for Data Guard</font></h2>  <a name="1017157"></a> <p class="BP">These practices build on the recommendations for configuring the single-instance database. The proper configuration of Oracle Data Guard Redo Apply and SQL Apply is essential to ensuring that all standby databases work properly and perform their roles within service levels after switchovers and failovers. Most Data Guard configuration settings can be made through the Oracle Enterpr ise Manager. For more advanced, less frequently used Data Guard configuration parameters, the Data Guard Broker command-line interfac e or SQL*Plus can be used.</p> <a name="1012663"></a> <p class="BP">Data Guard enables you to use either a physical standby database or a logical standby database or both, depending on the business requirements. A physical standby database provides a physically ide ntical copy of the primary database, with on-disk database structures that are identical to the primary database on a block-for-block basis. The database schema, including indexes, are the same. A physical standby database is kept synchronized with the primary datab ase by applying the redo data received from the primary database.</p> <a name="1012650"></a> <p class="BP">A logical standby databas e contains the same logical information as the production database, although the physical organization and structure of the data can be different. It is kept synchronized with the primary database by transforming the data in the redo log files received from the prim ary database into SQL statements and then executing the SQL statements on the standby database. A logical standby database can be use d for other business purposes in addition to disaster recovery requirements.</p> <a name="1008128"></a> <p class="BP"><a href="confi gbp.htm#1012729">Table 7-1</a> can help you determine which type of standby database to use.</p> <a name="1012726"></a> <h5 cla ss="TTW"><a name="1012726"></a><a name="1012729"></a> <strong><font face="Arial, Helvetica, sans-serif"><em>Table 7-1 Determining the Standby Database Type </em></font></strong></h5> <table summary="" class="HRuleFormalWide" border="1" frame="HSIDES" rules="RO WS" width="100%" cellpadding="3" cellspacing="0" dir="ltr" title=""> <thead> <tr class="Formal"> <th class="Formal" align="left" vali gn="bottom" scope="col"><a name="1012733"></a> <font face="Arial, Helvetica, sans-serif"><strong>Questions</strong></font></th> <th c lass="Formal" align="left" valign="bottom" scope="col"><a name="1012735"></a> <font face="Arial, Helvetica, sans-serif"><strong>Recom mendations</strong></font></th></tr></thead> <tbody> <tr class="Formal" align="left" valign="top"> <td class="Formal"> <ol class="TLN "> <li class="TLN" type="1" value="1"><a name="1012741"></a>Do you have any datatypes that are not supported by the logical standby d atabase?</li></ol></td> <td class="Formal"><a name="1012743"></a> <p class="TB">Run the following query:</p> <pre class="TCI"><a nam e="1012770"></a>SELECT DISTINCT OWNER, TABLE_NAME FROM DBA_LOGSTDBY_UNSUPPORTED ORDER BY OWNER, TABLE_NAME; </pre> <a name="101277 1"></a> <p class="TB">Rows returned - Use a physical standby database or investigate changing to supported datatypes <a name="1012772 "></a></p> <p class="TB">No rows returned - Go to next question</p></td></tr> <tr class="Formal" align="left" valign="top"> <td class ="Formal"> <ol class="TLN"> <li class="TLN" type="1" value="2"><a name="1012745"></a>Do you need to have the standby database open fo r read-only or read/write access?</li></ol> <a name="1016429"></a> <p class="TB"><strong class="Bold">See Also</strong>: "Oracle9<em class="Italic">i</em> Data Guard: SQL Apply Best Practices" at <code><a href="http://otn.oracle.com/deploy/availability/htdocs/maa.h tm">http://otn.oracle.com/deploy/availability/htdocs/maa.htm</a></code></p></td> <td class="Formal"><a name="1012747"></a> <p class= "TB">Yes - Evaluate a logical standby database <a name="1012773"></a></p> <p class="TB">No - Use a physical standby database</p></td> </tr></tbody></table> <a name="1012778"></a> <p class="BP"><a href="configbp.htm#1013342">Table 7-2</a> shows the recommendatio ns for configuration that apply to both logical and physical standby databases and those that apply to only logical and only physical .</p> <a name="1012783"></a> <h5 class="TTW"><a name="1012783"></a><a name="1013342"></a> <strong><font face="Arial, Helvetica, sans -serif"><em>Table 7-2 Recommendations for Configuring Standby Databases </em></font></strong></h5> <table summary="" class="For malWide" border="1" frame="HSIDES" rules="GROUPS" width="100%" cellpadding="3" cellspacing="0" dir="ltr" title=""> <thead> <tr class= "Formal"> <th class="Formal" align="left" valign="bottom" scope="col"><a name="1013348"></a> <font face="Arial, Helvetica, sans-serif "><strong>Recommendations for Both Physical and Logical Standby Databases</strong></font></th> <th class="Formal" align="left" valign ="bottom" scope="col"><a name="1013350"></a> <font face="Arial, Helvetica, sans-serif"><strong>Recommendations for Physical Standby D atabases Only</strong></font></th> <th class="Formal" align="left" valign="bottom" scope="col"><a name="1013352"></a> <font face="Ari al, Helvetica, sans-serif"><strong>Recommendations for Logical Standby Databases Only</strong></font></th></tr></thead> <tbody> <tr c lass="Formal" align="left" valign="top"> <td class="Formal"><a name="1013356"></a> <p class="TB"><a href="configbp.htm#1007094">Use a Simple, Robust Archiving Strategy and Configuration</a></p></td> <td class="Formal"><a name="1013359"></a> <p class="TB"><a href=" configbp.htm#1007363">Tune Media Recovery Performance</a></p></td> <td class="Formal"><a name="1013361"></a> <p class="TB"><a href=" configbp.htm#1013958">Use Supplemental Logging and Primary Key Constraints</a></p></td></tr> <tr class="Formal" align="left" valign=" top"> <td class="Formal"><a name="1013365"></a> <p class="TB"><a href="configbp.htm#1007148">Use Multiplexed Standby Redo Logs and C onfigure Size Appropriately</a></p></td> <td class="Formal"><a name="1013368"></a> <p class="TB">-</p></td> <td class="Formal"><a na me="1013370"></a> <p class="TB"><a href="configbp.htm#1013872">Set the MAX_SERVERS Initialization Parameter</a></p></td></tr> <tr cl ass="Formal" align="left" valign="top"> <td class="Formal"><a name="1013378"></a> <p class="TB"><a href="configbp.htm#1013147">Enabl e FORCE LOGGING Mode</a></p></td> <td class="Formal"><a name="1013380"></a> <p class="TB">-</p></td> <td class="Formal"><a name="101 3540"></a> <p class="TB"><a href="configbp.htm#1013997">Increase the PARALLEL_MAX_SERVERS Initialization Parameter</a></p></td></tr> <tr class="Formal" align="left" valign="top"> <td class="Formal"><a name="1013387"></a> <p class="TB"><a href="configbp.htm#1007157 ">Use Real Time Apply</a></p></td> <td class="Formal"><a name="1013389"></a> <p class="TB">-</p></td> <td class="Formal"><a name="10 13542"></a> <p class="TB"><a href="configbp.htm#1013878">Set the TRANSACTION_CONSISTENCY Initialization Parameter</a></p></td></tr> <tr class="Formal" align="left" valign="top"> <td class="Formal"><a name="1013431"></a> <p class="TB"><a href="configbp.htm#1007198" >Configure the Database and Listener for Dynamic Service Registration</a></p></td> <td class="Formal"><a name="1013434"></a> <p clas s="TB">-</p></td> <td class="Formal"><a name="1013758"></a> <p class="TB"><a href="configbp.htm#1013880">Skip SQL Apply for Unnecess ary Objects</a></p></td></tr> <tr class="Formal" align="left" valign="top"> <td class="Formal"><a name="1013458"></a> <p class="TB"> <a href="configbp.htm#1007220">Tune the Network in a WAN Environment</a></p></td> <td class="Formal"><a name="1013461"></a> <p class ="TB">-</p></td> <td class="Formal"><a name="1013463"></a> <p class="TB">-</p></td></tr> <tr class="Formal" align="left" valign="top "> <td class="Formal"><a name="1013467"></a> <p class="TB"><a href="configbp.htm#1007224">Determine the Data Protection Mode</a></p> </td> <td class="Formal"><a name="1013470"></a> <p class="TB">-</p></td> <td class="Formal"><a name="1013472"></a> <p class="TB">-< /p></td></tr> <tr class="Formal" align="left" valign="top"> <td class="Formal"><a name="1013476"></a> <p class="TB"><a href="configb p.htm#1007305">Conduct a Performance Assessment with the Proposed Network Configuration</a></p></td> <td class="Formal"><a name="1013 479"></a> <p class="TB">-</p></td> <td class="Formal"><a name="1013481"></a> <p class="TB">-</p></td></tr> <tr class="Formal" align ="left" valign="top"> <td class="Formal"><a name="1013485"></a> <p class="TB"><a href="configbp.htm#1007337">Use a LAN or MAN for Ma ximum Availability or Maximum Protection Modes</a></p></td> <td class="Formal"><a name="1013488"></a> <p class="TB">-</p></td> <td c lass="Formal"><a name="1013490"></a> <p class="TB">-</p></td></tr> <tr class="Formal" align="left" valign="top"> <td class="Formal"> <a name="1013494"></a> <p class="TB"><a href="configbp.htm#1007345">Set SYNC=NOPARALLEL/PARALLEL Appropriately</a></p></td> <td clas s="Formal"><a name="1013497"></a> <p class="TB">-</p></td> <td class="Formal"><a name="1013499"></a> <p class="TB">-</p></td></tr> <tr class="Formal" align="left" valign="top"> <td class="Formal"><a name="1013503"></a> <p class="TB"><a href="configbp.htm#1007349" >Use ARCH for the Greatest Performance Throughput</a></p></td> <td class="Formal"><a name="1013506"></a> <p class="TB">-</p></td> <t d class="Formal"><a name="1013508"></a> <p class="TB">-</p></td></tr> <tr class="Formal" align="left" valign="top"> <td class="Forma l"><a name="1013512"></a> <p class="TB"><a href="configbp.htm#1007351">Use the ASYNC Attribute with a 50 MB Buffer for Maximum Perfo rmance Mode</a></p></td> <td class="Formal"><a name="1013515"></a> <p class="TB">-</p></td> <td class="Formal"><a name="1013517"></a > <p class="TB">-</p></td></tr> <tr class="Formal" align="left" valign="top"> <td class="Formal"><a name="1013521"></a> <p class="T B"><a href="configbp.htm#1007361">Evaluate SSH Port Forwarding with Compression</a></p></td> <td class="Formal"><a name="1013524"></a > <p class="TB">-</p></td> <td class="Formal"><a name="1013526"></a> <p class="TB">-</p></td></tr> <tr class="Formal" align="left" valign="top"> <td class="Formal"><a name="1013528"></a> <p class="TB"><a href="configbp.htm#1013801">Set LOG_ARCHIVE_LOCAL_FIRST to TRUE</a></p></td> <td class="Formal"><a name="1013530"></a> <p class="TB">-</p></td> <td class="Formal"><a name="1013532"></a> <p c lass="TB">-</p></td></tr> <tr class="Formal" align="left" valign="top"> <td class="Formal"><a name="1013534"></a> <p class="TB"><a h ref="configbp.htm#1014587">Provide Secure Transmission of Redo Data</a></p></td> <td class="Formal"><a name="1013536"></a> <p class= "TB">-</p></td> <td class="Formal"><a name="1013538"></a> <p class="TB">-</p></td></tr> <tr class="Formal" align="left" valign="top" > <td class="Formal"><a name="1016460"></a> <p class="TB"><a href="configbp.htm#1016594">Set DB_UNIQUE_NAME</a></p></td> <td class=" Formal"><a name="1016462"></a> <p class="TB">-</p></td> <td class="Formal"><a name="1016464"></a> <p class="TB">-</p></td></tr> <tr class="Formal" align="left" valign="top"> <td class="Formal"><a name="1016454"></a> <p class="TB"><a href="configbp.htm#1016596">Se t LOG_ARCHIVE_CONFIG Correctly</a></p></td> <td class="Formal"><a name="1016456"></a> <p class="TB">-</p></td> <td class="Formal"><a name="1016458"></a> <p class="TB">-</p></td></tr></tbody></table> <a name="1008247"></a> <div align="center"> <table class="NoteAl so" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1008250"></a><font face="Arial, Helvetica, san s-serif"><strong class="NH">See Also:</strong></font> <a name="1008251"></a> <ul class="NL"> <li class="NL" type="disc"><a name="100 8253"></a><em class="Italic"><a class="olinkSRC SBYDB" href="../../server$101/b10823/toc.htm">Oracle Data Guard Concepts and Administ ration</a></em></li> <li class="NL" type="disc"><a name="1008259"></a><em class="Italic"><a class="olinkSRC REFRN" href="../../server $101/b10755/toc.htm">Oracle Database Reference</a></em></li></ul></td></tr></table></div> <a name="1007094"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Use a Simple, Robust Archiving Strategy and Configuratio n</font></h3>  <a name="1007095"></a> <p class="BP">This archiving strategy is based on the following assumptions:</p> <ul class="LB1"> <li class="LB1" type="disc"><a name="1007096"></a>Every instance uses the flash recovery area.</li> <li class="LB1" type="disc"><a name="1007097"></a>The production instances archive remotely to only one apply instance.</li></ul> <a name="1007098"> </a> <p class="BP"><a href="configbp.htm#1011409">Table 7-3</a> describes the recommendations for a robust archiving strategy.< /p> <a name="1011406"></a> <h5 class="TTW"><a name="1011406"></a><a name="1011409"></a> <strong><font face="Arial, Helvetica, sans-s erif"><em>Table 7-3 Archiving Recommendations </em></font></strong></h5> <table summary="" class="HRuleFormalWide" border="1" f rame="HSIDES" rules="ROWS" width="100%" cellpadding="3" cellspacing="0" dir="ltr" title=""> <thead> <tr class="Formal"> <th class="Fo rmal" align="left" valign="bottom" scope="col"><a name="1011413"></a> <font face="Arial, Helvetica, sans-serif"><strong>Recommendatio n</strong></font></th> <th class="Formal" align="left" valign="bottom" scope="col"><a name="1011415"></a> <font face="Arial, Helvetic a, sans-serif"><strong>Description</strong></font></th></tr></thead> <tbody> <tr class="Formal" align="left" valign="top"> <td class= "Formal"><a name="1011451"></a> <p class="TB">Archiving must be started on the primary database</p></td> <td class="Formal"><a name= "1011453"></a> <p class="TB">Maintaining a standby database requires archiving to be enabled and started on the primary database.</p > <pre class="TCI"><a name="1013110"></a>SQL> SHUTDOWN IMMEDIATE <a name="1013111"></a>SQL> STARTUP MOUNT; <a name="1013112"></ a>SQL> ALTER DATABASE ARCHIVELOG; <a name="1013113"></a>SQL> ALTER DATABASE OPEN; </pre> </td></tr> <tr class="Formal" align="l eft" valign="top"> <td class="Formal"><a name="1013115"></a> <p class="TB">Remote archiving must be enabled.</p></td> <td class="Form al"><a name="1013117"></a> <p class="TB"><code>REMOTE_ARCHIVE_ENABLE=TRUE</code></p></td></tr> <tr class="Formal" align="left" valig n="top"> <td class="Formal"><a name="1011455"></a> <p class="TB">Use a consistent log format (<code>LOG_ARCHIVE_FORMAT</code>).</p>< /td> <td class="Formal"><a name="1011457"></a> <p class="TB"><code>LOG_ARCHIVE_FORMAT</code> should have the thread, sequence, and r esetlogs ID attributes and should be consistent across all instances. <code>%S</code> instructs the format to fill the prefix of the sequence number with leading zeros. <a name="1017140"></a></p> <p class="TB">If the flash recovery is used, then this format is ignor ed. <a name="1013122"></a></p> <p class="TB">For example: <code>LOG_ARCHIVE_FORMAT=arch_%t_%S_%r.arc</code></p></td></tr> <tr class=" Formal" align="left" valign="top"> <td class="Formal"><a name="1016149"></a> <p class="TB">Local archiving is done first by the arch iver process (<code>ARCH</code>).</p></td> <td class="Formal"><a name="1016151"></a> <p class="TB">Using <code>ARCH</code> reduces t he work for <code>LGWR</code>. The default setting for <code>LOG_ARCHIVE_LOCAL_FIRST</code> is <code>TRUE</code>, which means that af ter the redo log has been completely and successfully archived to at least one local destination, it will then be transmitted to the remote destination. Using the flash recovery area implies that <code>LOG_ARCHIVE_DEST_10</code> is used for local archiving.</p></td> </tr> <tr class="Formal" align="left" valign="top"> <td class="Formal"><a name="1011470"></a> <p class="TB">Remote archiving should be done to only one standby instance and node for each standby RAC database.</p></td> <td class="Formal"><a name="1011472"></a> <p c lass="TB">All production instances archive to one standby destination, using the same net service name. Oracle Net Services connect-t ime failover is used if you want to automatically switch to the secondary standby host when the primary standby instance has an outag e.</p></td></tr> <tr class="Formal" align="left" valign="top"> <td class="Formal"><a name="1016161"></a> <p class="TB">The standby a rchive destination should use the flash recovery area.</p></td> <td class="Formal"><a name="1016163"></a> <p class="TB">For simplici ty, the standby archive destination (<code>STANDBY_ARCHIVE_DEST</code>) should use the flash recovery area, which is the same as the directory for the local archiving. Because SRLs are present, the standby <code>ARCH</code> process writes to the local archive destin ation.</p></td></tr> <tr class="Formal" align="left" valign="top"> <td class="Formal"><a name="1016473"></a> <p class="TB">The logic al standby archive destination cannot use the flash recovery area.</p></td> <td class="Formal"><a name="1016475"></a> <p class="TB"> For a logical standby database, <code>STANDBY_ARCHIVE_DEST</code> cannot use the flash recovery area. Set <code>STANDBY_ARCHIVE_DEST< /code> to an explicit archive directory.</p></td></tr> <tr class="Formal" align="left" valign="top"> <td class="Formal"><a name="1017 149"></a> <p class="TB">Specify role-based destinations with the <code>VALID_FOR</code> attribute</p></td> <td class="Formal"><a nam e="1017151"></a> <p class="TB">The <code>VALID_FOR</code> attribute enables you to configure destination attributes for both the pri mary and the standby database roles in one server parameter file (SPFILE), so that the Data Guard configuration operates properly aft er a role transition. This simplifies switchovers and failovers by removing the need to enable and disable the role-specific paramete r files after a role transition. <a name="1017172"></a></p> <p class="TB"><strong class="Bold">See Also:</strong> <a href="appconfig. htm#620714">Appendix B, "Database SPFILE and Oracle Net Configuration File Samples"</a></p></td></tr></tbody></table> <a name="1 007122"></a> <p class="BP">The following example illustrates the recommended initialization parameters for a primary database commun icating to a physical standby database. There are two instances, <code>SALES1</code> and <code>SALES2</code>, running in maximum prot ection mode.</p> <pre class="CE"><a name="1007131"></a>*.DB_RECOVERY_FILE_DEST=/recoveryarea <a name="1016173"></a>*LOG_ARCHIVE_DEST_ 1='SERVICE=SALES LGWR SYNC=NOPARALLEL AFFIRM <a name="1016176"></a> REOPEN=15 MAX_FAILURE=10 VALID_FOR=(ONLINE+LOGFILES, ALL ROLES )' <a name="1016177"></a>*.LOG_ARCHIVE_DEST_STATE_1='ENABLE' <a name="1016178"></a>*.STANDBY_ARCHIVE_DEST='USE_DB_RECOVERY_FILE_DEST' <a name="1016175"></a> </pre> <a name="1007132"></a> <p class="BP">Note the following observations for this example:</p> <ul class= "LB1"> <li class="LB1" type="disc"><a name="1007133"></a>The <code>PARALLEL</code> attribute is used when there are multiple standby destinations. When <code>SYNC</code> is set to <code>PARALLEL</code>, the <code>LGWR</code> process initiates an I/O operation to eac h standby destination at the same time. Because there is a single standby destination, the <code>NOPARALLEL</code> option is set to r educe overhead.</li> <li class="LB1" type="disc"><a name="1007134"></a>The <code>REOPEN=15 MAX_FAILURE=10</code> setting denotes that if there is a connection failure, then the connection is reopened after 15 seconds and is retried up to 10 times.</li> <li class="LB 1" type="disc"><a name="1007138"></a>The <code>VALID_FOR</code> clause is used to designate the role for a destination. When the data base is in a physical standby role, remote destination <code>LOG_ARCHIVE_DEST_1</code> is not used because a physical standby databas e does not use online log files.</li></ul> <a name="1007142"></a> <p class="BP">The flash recovery area must be accessible to any no de within the cluster and use a shared file system technology such as automatic storage management (ASM), a cluster file system, a gl obal file system, or high availability network file system (HA NFS). You can also mount the file system manually to any node within t he cluster very quickly. This is necessary for recovery because all archived redo log files must be accessible on all nodes.</p> <a n ame="1013132"></a> <p class="BP">On the standby database nodes, recovery from a different node is required when Node 1 fails and can not be restarted. In that case, any of the existing standby instances residing on a different node can initiate managed recovery. In the worst case, when the standby archived redo log files are inaccessible, the new managed recovery process (MRP) or logical standby process (LSP) on the different node fetches the archived redo log files using the FAL server to retrieve from the production nodes di rectly.</p> <a name="1007144"></a> <p class="BP">When configuring hardware vendor shared file system technology, verify the performa nce and availability implications. Investigate the following issues before adopting this strategy:</p> <ul class="LB1"> <li class="LB 1" type="disc"><a name="1007145"></a>Is the shared file system accessible by any node regardless of the number of node failures?</li> <li class="LB1" type="disc"><a name="1007146"></a>What is the performance impact when implementing a shared file system?</li> <li cl ass="LB1" type="disc"><a name="1007147"></a>Is there any impact on the interconnect traffic?</li></ul> <a name="1007148"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Use Multiplexed Standby Redo Logs and Confi gure Size Appropriately</font></h3>  <a name="1007149"></a> <p class="BP">Standby redo logs (SRLs) should be used on b oth sites. Use Oracle log multiplexing to create multiple standby redo log members in each standby redo group. This protects against a failure involving the redo log, such as disk corruption that exists on both sides of the disk mirror for one of the members or a us er error that accidentally removed a member.</p> <a name="1013144"></a> <p class="BP">Use this formula to determine the number of SR Ls:</p> <pre class="CEM"><a name="1007150"></a># of SRLs = sum of all production online log groups per thread + number of threads </p re> <pre class="CE"><a name="1007151"></a> </pre> <a name="1007152"></a> <p class="BP">For example, if a primary database has two i nstances (threads) and each thread has four online log groups, then there should be ten SRLs. Having one more standby log group for e ach thread than the number of the online redo log groups for the production database reduces the likelihood that the <code>LGWR</code > for the production instance is blocked because an SRL cannot be allocated on the standby.</p> <a name="1008866"></a> <p class="BP" >The following are additional guidelines for creating SRLs:</p> <ul class="LB1"> <li class="LB1" type="disc"><a name="1007153"></a>Cr eate the same number of SRLs for both production and standby databases.</li> <li class="LB1" type="disc"><a name="1007154"></a>All of the online redo logs and SRLs for both the production and the standby databases should be the same size.</li> <li class="LB1" type=" disc"><a name="1008870"></a>The SRLs should exist on both production and standby databases.</li> <li class="LB1" type="disc"><a name= "1016067"></a>In a RAC environment, the SRLs must be on a shared disk.</li> <li class="LB1" type="disc"><a name="1016478"></a>In a RA C environment, assign the SRL to a thread when the SRL is created. For example: <pre class="CE"><a name="1016479"></a> ALTER DATA BASE ADD STANDBY LOGFILE THREAD 1 GROUP 10 <a name="1016480"></a> '/dev/vx/rdsk/ha10-dg/DGFUN stbyredo10 01.log' SIZE 50M REUS E; <a name="1016481"></a> </pre> </li></ul> <a name="1008871"></a> <p class="BP">The remote file server (RFS) process for the standby database writes only to an SRL whose size is identical to the size of an online redo log for the production database. If it cannot f ind an appropriately sized SRL, then RFS creates an archived redo log file directly instead and logs the following message in the ale rt log:</p> <pre class="CE"><a name="1008878"></a>No standby redo log files of size <#> blocks available. </pre> <a name="1013 147"></a> <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Enable FORCE LOGGING Mode</ font></h3>  <a name="1013150"></a> <p class="BP">When the production database is in <code>FORCE LOGGING</code> mode, a ll database changes are logged except for those in temporary tablespaces and temporary segments. <code>FORCE LOGGING</code> mode ensu res that the standby database remains consistent with the production database. If this is not possible because you require the load p erformance with <code>NOLOGGING</code> operations, then you must ensure that the corresponding standby datafiles are subsequently syn chronized. After completing the nologging operations, a production backup of the affected datafiles needs to replace the correspondin g standby datafiles. Before the file transfer, the physical standby database must stop recovery and the logical standby database must temporarily take the affected tablespaces offline.</p> <a name="1013151"></a> <p class="BP">You can enable force logging immediatel y by issuing an <code>ALTER DATABASE FORCE LOGGING</code> statement. If you specify <code>FORCE LOGGING</code>, then Oracle waits for all ongoing unlogged operations to finish.</p> <a name="1013148"></a> <div align="center"> <table class="NoteAlso" border="0" width ="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to f ormat a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1013156"></a><font face="Arial, Helvetica, sans-serif"><strong cla ss="NH">See Also:</strong></font> <a name="1013157"></a> <ul class="NL"> <li class="NL" type="disc"><a name="1013176"></a><em class= "Italic"><a class="olinkSRC ADMIN" href="../../server$101/b10739/toc.htm">Oracle Database Administrator's Guide</a></em></li> <li cla ss="NL" type="disc"><a name="1013159"></a><em class="Italic"><a class="olinkSRC SBYDB" href="../../server$101/b10823/toc.htm">Oracle Data Guard Concepts and Administration</a></em></li></ul></td></tr></table></div> <a name="1007157"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Use Real Time Apply</font></h3>  <a name="1013728" ></a> <p class="BP">Using real time apply enables the log apply services to apply redo data (physical standby database) or SQL (logi cal standby database) as it is received without waiting for the current standby redo log file to be archived. This results in faster switchover and failover times because the standby redo log files are applied to the standby database before failover or switchover be gins.</p> <a name="1014582"></a> <p class="BP">For a physical standby database, use the following SQL statement</p> <pre class="CE"> <a name="1013729"></a>ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE; <a name="1014583"></a> </pre> <a name=" 1014584"></a> <p class="BP">For a logical standby database, use the following SQL statement:</p> <pre class="CE"><a name="1014586"></ a>ALTER DATABASE START LOGICAL STANDBY APPLY IMMEDIATE; </pre> <a name="1013730"></a> <div align="center"> <table class="NoteAlso" b order="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a la yout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1013733"></a><font face="Arial, Helvetica, sans-ser if"><strong class="NH">See Also:</strong></font> <a name="1013734"></a> <p class="NB"><em class="Italic"><a class="olinkSRC SBYDB" h ref="../../server$101/b10823/toc.htm">Oracle Data Guard Concepts and Administration</a></em></p></td></tr></table></div> <a name="100 7198"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Configure the Database an d Listener for Dynamic Service Registration</font></h3>  <a name="1007199"></a> <p class="BP">The setting for the <cod e>SERVICE</code> attribute of the <code>LOG_ARCHIVE_DEST_2</code> initialization parameter and the settings for the <code>FAL_SERVER< /code> and <code>FAL_CLIENT</code> initialization parameters depend on a proper Oracle Net configuration. For the Oracle Data Guard t ransport service and the gap resolution feature to work, the <code>SPFILE</code>, <code>listener.ora</code>, <code>tnsnames.ora</code >, and <code>sqlnet.ora</code> files must be consistent.</p> <a name="1009088"></a> <div align="center"> <table class="NoteAlso" bor der="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layo ut table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1009091"></a><font face="Arial, Helvetica, sans-serif "><strong class="NH">See Also:</strong></font> <a name="1017195"></a> <ul class="NL"> <li class="NL" type="disc"><a name="1017675">< /a><a href="appconfig.htm#620714">Appendix B, "Database SPFILE and Oracle Net Configuration File Samples"</a></li> <li class="NL " type="disc"><a name="1017684"></a>MetaLink Note 76636.1 at <code><a href="http://metalink.oracle.com">http://metalink.oracle.com</a ></code></li></ul></td></tr></table></div> <a name="1007200"></a> <p class="BP">The remote archive destination <code>FAL_CLIENT</cod e> and <code>FAL_SERVER</code> parameters require an Oracle Net service. This service is represented as a net service name entry in t he local <code>tnsnames.ora</code> file. Notice that the <code>FAL_SERVER</code> and <code>FAL_CLIENT</code> reference the same Oracl e network service name. This is possible because the <code>FAL_SERVER</code> service is defined in the standby <code>tnsnames.ora</co de> file, whereas the <code>FAL_CLIENT</code> service is defined in the primary <code>tnsnames.ora</code> file. This works only when you use the Oracle Network Service local naming method. If you are not using the local naming method, then you must have different se rvice names. Furthermore, Oracle recommends using dynamic service registration instead of a static SID list in the listener configura tion. To ensure that service registration works properly, the server parameter file should contain the following parameters:</p> <ul class="LB1"> <li class="LB1" type="disc"><a name="1007201"></a><code>SERVICE_NAMES</code> for the database service name</li> <li clas s="LB1" type="disc"><a name="1007202"></a><code>INSTANCE_NAME</code> for the instance name</li> <li class="LB1" type="disc"><a name=" 1007203"></a><code>LOCAL_LISTENER</code> to specify a nondefault listener address</li></ul> <a name="1007204"></a> <p class="BP"><co de>PMON</code> dynamically registers a database service with the listener. <code>PMON</code> attempts to resolve <code>LOCAL_LISTENER </code> using some naming method. In the case described here, <code>PMON</code> finds the corresponding name in the local <code>tnsna mes.ora</code> file.</p> <a name="1007205"></a> <p class="BP">For example:</p> <pre class="CEM"><a name="1007206"></a>SALES1.INSTANC E_NAME='SALES1' <a name="1007207"></a>SALES2.INSTANCE_NAME='SALES2' <a name="1007208"></a>*.LOG_ARCHIVE_DEST_2='SERVICE=SALES LGWR SY NC=NOPARALLEL AFFIRM REOPEN=15 MAX_FAILURE=10' <a name="1007209"></a>*.LOCAL_LISTENER='SALES_lsnr' <a name="1007210"></a>*.SERVICE_NA MES='SALES' # required for service registration <a name="1007211"></a>*.FAL_SERVER='SALES' <a name="1007212"></a>*.FAL_CLIENT='SAL ES' </pre> <pre class="CE"><a name="1007213"></a> </pre> <a name="1007214"></a> <p class="BP">The <code>listener.ora</code> file sh ould be identical for each primary and secondary host except for <code>HOST</code> settings. Because service registration is used, th ere is no need for statically configured information.</p> <a name="1007215"></a> <p class="BP">The local <code>tnsnames.ora</code> f ile should contain the net service names and the local listener name translation. To use the same service name on each node, you must use a locally managed <code>tnsnames.ora</code> file for the production and standby databases. On the primary cluster, the <code>tns names.ora</code> entry, <code>SERVICE_NAME</code>, should equal the setting of the <code>SERVICE_NAMES SPFILE</code> parameter. If th e listener is started after the instance, then service registration does not happen immediately. In this case, issue the <code>ALTER SYSTEM REGISTER</code> statement on the database to instruct the <code>PMON</code> background process to register the instance with t he listeners immediately.</p> <a name="1009142"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding ="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1009148"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:< /strong></font> <a name="1009150"></a> <p class="NB"><em class="Italic"><a class="olinkSRC NETAG" href="../../network$101/b10775/toc .htm">Oracle Net Services Administrator's Guide</a></em></p></td></tr></table></div> <a name="1007220"></a>  < h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Tune the Network in a WAN Environment</font></h3>  <a name="1007221"></a> <p class="BP">Reducing the number of round trips across the network is essential for optimizing the trans portation of redo log data to a standby site. With Oracle Net Services it is possible to control data transfer by adjusting the size of the Oracle Net setting for the session data unit (SDU). In a WAN environment, setting the SDU to 32K can improve performance. The SDU parameter designates the size of an Oracle Net buffer before it delivers each buffer to the TCP/IP network layer for transmission across the network. Oracle Net sends the data in the buffer either when requested or when it is full. Oracle internal testing of Ora cle Data Guard on a WAN has demonstrated that the maximum setting of 32K (32768) performs best on a WAN. The primary gain in performa nce when setting the SDU is a result of the reduced number of calls to packet the data.</p> <a name="1007223"></a> <p class="BP">In addition to setting the <code>SDU</code> parameter, network throughput can often be substantially improved by using the <code>SQLNET. SEND_BUF_SIZE</code> and <code>SQLNET.RECV_BUF_SIZE</code> Oracle Net parameters to increase the size of the network TCP send and rec eive I/O buffers.</p> <a name="1009195"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cel lspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class=" NoteAlso"> <td class="NoteAlso"><a name="1009199"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong> </font> <a name="1016488"></a> <p class="NB"><em class="Italic"><a class="olinkSRC NETAG" href="../../network$101/b10775/toc.htm">Or acle Net Services Administrator's Guide</a></em></p></td></tr></table></div> <a name="1007224"></a>  <h3 class ="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Determine the Data Protection Mode</font></h3>  <a name ="1007225"></a> <p class="BP">In some situations, a business cannot afford to lose data at any cost. In other situations, the availa bility of the database may be more important than protecting f data. Some applications require maximum database performance and can t olerate a potential loss of data if a disaster occurs.</p> <a name="1007226"></a> <p class="BP">Choose one of the following protecti on modes:</p> <ul class="LB1"> <li class="LB1" type="disc"><a name="1007227"></a><strong class="Bold">Maximum protection mode</strong > guarantees that no data loss will occur if the primary database fails. To ensure that data loss cannot occur, the primary database shuts down if a fault prevents it from writing its redo stream to at least one remote standby redo log.</li> <li class="LB1" type="di sc"><a name="1007228"></a><strong class="Bold">Maximum availability mode</strong> provides the highest level of data protection that is possible without compromising the availability of the primary database.</li> <li class="LB1" type="disc"><a name="1007229"></a><st rong class="Bold">Maximum performance mode</strong> (the default mode) provides the highest level of data protection that is possible without affecting the performance of the primary database. This is accomplished by allowing a transaction to commit as soon as the r edo data needed to recover that transaction is written to the local online redo log. The redo data stream of the primary database is also written to at least one standby database, but that redo stream is written asynchronously with respect to the commitment of the t ransactions that create the redo data. When network links with sufficient bandwidth are used, this mode provides a level of data prot ection that approaches that of maximum availability mode with minimal impact on primary database performance.</li></ul> <a name="1007 230"></a> <p class="BP">This section includes the following topics:</p> <ul class="LB1"> <li class="LB1" type="disc"><a name="100723 3"></a><a href="configbp.htm#1007260">Determining the Protection Mode</a></li> <li class="LB1" type="disc"><a name="1009227"></a><a h ref="configbp.htm#1007285">Changing the Data Protection Mode</a> <p><a name="1016548"></a></p> <div align="center"> <table class="No teAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="Thi s is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1016551"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1016552"></a> <p class="NB"><em class="Italic"><a class="xlinkSRC SBYDB00439" href="../../server$101/b10823/concepts.htm#SBYDB00439">Oracle Data Guard Concepts and Administration</a></em> for more i nformation about data protection modes</p></td></tr></table></div></li></ul> <a name="1007260"></a>  <h4 class ="H3"><font face="Arial, Helvetica, sans-serif" color="#330099">Determining the Protection Mode</font></h4>  <a name="1 007261"></a> <p class="BP">To determine the correct data protection mode for your application, ask the questions in <a href="configb p.htm#1011570">Table 7-4</a>.</p> <a name="1011567"></a> <h5 class="TTW"><a name="1011567"></a><a name="1011570"></a> <strong>< font face="Arial, Helvetica, sans-serif"><em>Table 7-4 Determining the Appropriate Protection Mode </em></font></strong></h5> < table summary="" class="HRuleFormalWide" border="1" frame="HSIDES" rules="ROWS" width="100%" cellpadding="3" cellspacing="0" dir="ltr " title=""> <thead> <tr class="Formal"> <th class="Formal" align="left" valign="bottom" scope="col"><a name="1011574"></a> <font face ="Arial, Helvetica, sans-serif"><strong>Question</strong></font></th> <th class="Formal" align="left" valign="bottom" scope="col"><a name="1011576"></a> <font face="Arial, Helvetica, sans-serif"><strong>Recommendations</strong></font></th></tr></thead> <tbody> <tr c lass="Formal" align="left" valign="top"> <td class="Formal"><a name="1011605"></a> <p class="TB">Is data loss acceptable if the prim ary site fails?</p></td> <td class="Formal"><a name="1011607"></a> <p class="TB">Yes: Use any protection mode. <a name="1011608"></a ></p> <p class="TB">No: Use maximum protection or maximum availability modes.</p></td></tr> <tr class="Formal" align="left" valign="t op"> <td class="Formal"><a name="1011610"></a> <p class="TB">How much data loss is tolerated if a site is lost?</p></td> <td class=" Formal"><a name="1011612"></a> <p class="TB">None: Use maximum protection or maximum availability modes. <a name="1011613"></a></p> <p class="TB">Some: Use maximum performance mode with <code>ASYNC=</code><em><code>blocks</code></em>. The value for the number of bl ocks determines the maximum amount of possible redo data loss if a site fails.</p></td></tr> <tr class="Formal" align="left" valign=" top"> <td class="Formal"><a name="1011615"></a> <p class="TB">Is potential data loss between the production and the standby database s tolerated when a standby host or network connection is temporarily unavailable?</p></td> <td class="Formal"><a name="1011617"></a> <p class="TB">Yes: Use maximum performance or maximum availability modes. <a name="1011618"></a></p> <p class="TB">No: Use maximum p rotection mode.</p></td></tr> <tr class="Formal" align="left" valign="top"> <td class="Formal"><a name="1011620"></a> <p class="TB"> How far away should the disaster recovery site be from the primary site?</p></td> <td class="Formal"><a name="1011622"></a> <p class ="TB">The distance between sites and the network infrastructure between the sites determines network latency. In general, the latency increases with distance. Determine the minimum distance between sites to provide for outage isolation and minimal network latency. A ssess what data centers are available for your company, or assess Oracle outsourcing services.</p></td></tr> <tr class="Formal" align ="left" valign="top"> <td class="Formal"><a name="1011624"></a> <p class="TB">What is the current or proposed network bandwidth and latency between sites?</p></td> <td class="Formal"><a name="1011626"></a> <p class="TB">Bandwidth must be greater than maximum redo generation rate. A guideline for two-way communication is for bandwidth to be 50 percent of the stated line capacity, but you must co nsider network usage of other applications. <a name="1011627"></a></p> <p class="TB">Using maximum performance mode with asynchronous log transport or the archiver mitigates the effect on performance.</p></td></tr></tbody></table> <a name="1007285"></a>  <h4 class="H3"><font face="Arial, Helvetica, sans-serif" color="#330099">Changing the Data Protection Mode</font></h4> <! --/TOC=h3--> <a name="1016570"></a> <p class="BP">The default data protection mode is maximum performance mode. After a failover to the standby database, the protection mode automatically changes to maximum performance mode. Switchover operations do not change the protection mode.</p> <a name="1016288"></a> <p class="BP">To change the data protection mode from maximum performance to maximum ava ilability or maximum protection, perform the following steps:</p> <ol class="LN1" type="1"> <li class="LN1" type="1" value="1"><a nam e="1007287"></a>Change the appropriate initialization parameters. For maximum protection and maximum availability modes, Oracle requi res one functional remote or standby archive destination using the <code>LGWR SYNC</code> option and a valid net service name during startup. For maximum performance mode, use the <code>LGWR ASYNC</code> option with a valid net service name.</li> <li class="LN1" typ e="1" value="2"><a name="1017568"></a>Shut down the primary database and restart it in mounted mode.</li> <li class="LN1" type="1" va lue="3"><a name="1007291"></a>Shut down all instances and start a single instance in exclusive mode. <pre class="CE1"><a name="10072 92"></a>SHUTDOWN IMMEDIATE; <a name="1007293"></a>STARTUP MOUNT EXCLUSIVE; <a name="1007294"></a> </pre> </li> <li class="LN1" type=" 1" value="4"><a name="1007295"></a>Change the data protection mode explicitly to the desired mode <pre class="CE1"><a name="1007296" ></a>ALTER DATABASE SET STANDBY TO MAXIMIZE [AVAILABILITY | PROTECTION]; <a name="1016512"></a> </pre> </li> <li class="LN1" type="1" value="5"><a name="1007302"></a>Restart all instances.</li></ol> <a name="1007304"></a> <p class="BP">To change the protection mode from maximum protection to maximum performance or maximum availability, use a statement similar to the following:</p> <pre class="CE "><a name="1016591"></a>ALTER DATABASE SET STANDBY TO MAXIMIZE [PERFORMANCE | AVAILABILITY]; </pre> <a name="1016291"></a> <div alig n="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1016294"></a>< font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1016295"></a> <ul class="NL"> <li cla ss="NL" type="disc"><a name="1016296"></a><em class="Italic"><a class="xlinkSRC SBYDB00430" href="../../server$101/b10823/log_transpo rt.htm#SBYDB00430">Oracle Data Guard Concepts and Administration</a></em> for more information about setting the data protection mode for a Data Guard configuration</li> <li class="NL" type="disc"><a name="1016302"></a><em class="Italic"><a class="xlinkSRC SBYDB0173 0" href="../../server$101/b10823/rac_support.htm#SBYDB01730">Oracle Data Guard Concepts and Administration</a></em> for more informat ion about changing the protection mode in a Data Guard and RAC configuration</li></ul></td></tr></table></div> <a name="1007305"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Conduct a Performance Assessment wi th the Proposed Network Configuration</font></h3>  <a name="1007306"></a> <p class="BP">Oracle recommends that you con duct a performance assessment with your proposed network configuration and current (or anticipated) peak redo rate. The network impac t between the production and standby databases and the impact on the primary database throughput needs to be understood. Because the network between the production and standby databases is essential for the two databases to remain synchronized, the infrastructure mu st have the following characteristics:</p> <ul class="LB1"> <li class="LB1" type="disc"><a name="1007307"></a>Sufficient bandwidth to accommodate the maximum redo generation rate</li> <li class="LB1" type="disc"><a name="1007308"></a>Minimal latency to reduce the pe rformance impact on the production database</li> <li class="LB1" type="disc"><a name="1007309"></a>Multiple network paths for network redundancy</li></ul> <a name="1007310"></a> <p class="BP">The required bandwidth of a dedicated network connection is determined by the maximum redo rate of the production database. You also need to account for actual network efficiency. Depending on the data prot ection mode, there are other recommended practices and performance considerations. Maximum protection mode and maximum availability m ode require <code>LGWR SYNC</code> transport. Maximum performance protection mode uses the <code>ASYNC</code> transport option or the archiver (<code>ARCH</code><em><code>n</code></em>) instead of <code>LGWR</code> to transfer the redo. These recommendations were de rived from an Oracle internal performance study that measured the impact of network latency on primary database throughput for each O racle Data Guard transport option: <code>ARCH</code>, <code>LGWR ASYNC,</code> and <code>LGWR SYNC</code>.</p> <a name="1009427"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a la yout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="100 9431"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1009432"></a> <p class="NB "><code><a href="http://otn.oracle.com/deploy/availability/htdocs/maa.htm">http://otn.oracle.com/deploy/availability/htdocs/maa.htm</ a></code> for details of the study</p></td></tr></table></div> <a name="1007311"></a> <p class="BP">The network infrastructure betwe en the primary and secondary sites must be able to accommodate the redo traffic because the production database redo data is updating the physical standby database. If your maximum redo traffic at peak load is 8 MB/second, then your network infrastructure must have sufficient bandwidth to handle this load. Furthermore, network latency affects overall throughput and response time for OLTP and batc h operations.</p> <a name="1007312"></a> <p class="BP">When you compare maximum protection mode or maximum availability mode with <c ode>LGWR SYNC</code> operations with maximum performance mode with <code>LGWR ASYNC</code> operations, measure whether performance or throughput will be degraded due to the incurred latency. You should also check whether the new throughput and response time are with in your application performance requirements. Distance and the network configuration directly influence latency, while high latency m ay slow down your potential transaction throughput and increase response time. The network configuration, number of repeaters, the ov erhead of protocol conversions, and the number of routers also affect the overall network latency and transaction response time.</p> <a name="1007337"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Use a LAN or MAN for Maximum Availability or Maximum Protection Modes</font></h3>  <a name="1007338"></a> <p class="BP">Maximum ava ilability mode or maximum protection mode require the Oracle Data Guard transport service to use the <code>LGWR SYNC</code> transport option. Network latency is an additional overhead for each <code>LGWR SYNC</code> I/O operation. <a href="configbp.htm#1009619">Figu re 7-1</a> shows that <code>LGWR SYNC</code> writes both locally to the online redo log and remotely through the network to the <code>RFS</code> process to the standby redo logs.</p> <a name="1009619"></a> <h4 class="FT"><font face="Arial, Helvetica, sans-seri f"><em>Figure 7-1 LGWR SYNC Operation</em></font></h4> <a name="1009622"><img src="maxav005.gif" alt="Text description of maxav005.gi f follows"></a> <p><a href="img_text/maxav005.htm">Text description of the illustration maxav005.gif</a></p> <a name="1009614"></a> <p class="BP">The following formulas emphasize that the remote write is always slower than the local write and is the limiting facto r when <code>LGWR</code> synchronous writes are occurring.</p> <pre class="CEM"><a name="1007339"></a>Local write = local write I/O t ime <a name="1007340"></a>Remote write = network round trip time (RTT) + local write I/O time (on standby machine) <a name="1009591"> </a> </pre> <a name="1007341"></a> <p class="BP">Using an example in which the network round trip time (RTT) is 20 milliseconds and <code>LGWR</code> synchronous write is configured, every transaction commit time increases by 20 milliseconds. This overhead impacts response time and may affect primary database throughput. Because of the additional overhead incurred by the RTT, a local area networ k (LAN) or a metropolitan area network (MAN) with an RTT less than or equal to 10 milliseconds should be used for applications that c annot tolerate a change in performance or response time. Whether to use a LAN or MAN depends on the results of the performance assess ment.</p> <a name="1007345"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Set SYNC=NOPARALLEL/PARALLEL Appropriately</font></h3>  <a name="1007346"></a> <p class="BP">With only one remote standby destination within a LAN, with sufficient bandwidth and low latency, Oracle recommends the <code>LGWR SYNC=NOPARALLEL AFFIRM</code> option for the best performance with maximum data protection capabilities. When no data loss is required and there is only one remote archive destination, <code>SYNC=NOPARALLEL</code> performs better than <code>SYNC=PARALLEL</code> (the default) with a single standb y destination.</p> <a name="1007347"></a> <p class="BP">If <code>SYNC=PARALLEL</code> is used, then the network I/O is initiated asy nchronously, so that I/O to multiple destinations can be initiated in parallel. However, after the I/O is initiated, <code>LGWR</code > waits for each I/O operation to complete before continuing. This is, in effect, the same as performing multiple synchronous I/O ope rations simultaneously. If the Data Guard configuration has more than one standby database, then use a cascading standby architecture to minimize overhead to the primary database. If business requirements stipulate that the production database must transfer to multi ple standby databases, then set <code>SYNC=PARALLEL</code>.</p> <a name="1016120"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a l ayout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1016123"></a><font face="Arial, Helvetica, sans-se rif"><strong class="NH">See Also:</strong></font> <a name="1016124"></a> <ul class="NL"> <li class="NL" type="disc"><a name="1016130 "></a><em class="Italic"><a class="olinkSRC SBYDB" href="../../server$101/b10823/toc.htm">Oracle Data Guard Concepts and Administrati on</a></em> for more information about cascading standby databases</li> <li class="NL" type="disc"><a name="1016131"></a>"Oracle9<em class="Italic">i</em> Data Guard: Primary Site and Network Configuration Best Practices" at <code><a href="http://otn.oracle.com/depl oy/availability/pdf/MAA_DG_NetBestPrac.pdf">http://otn.oracle.com/deploy/availability/pdf/MAA_DG_NetBestPrac.pdf</a></code>. These pr actices continue to apply to Oracle Database 10<em class="Italic">g</em>.</li></ul></td></tr></table></div> <a name="1007349"></a> <! --TOC=h2-"1007349"--> <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Use ARCH for the Greatest Performance Throughput</font></h3>  <a name="1007350"></a> <p class="BP">The <code>ARCH</code> attribute of the <code>LOG_ARCHIVE_ DEST_</code><em><code>n</code></em> initialization parameter provides the greatest performance throughput but the greatest data loss potential. <code>ARCH</code> does not affect primary performance when latency increases as long as the redo logs are configured corre ctly as described in <a href="configbp.htm#1006921">"Configure the Size of Redo Log Files and Groups Appropriately"</a><a href="confi gbp.htm#1006921"></a>. This is recommended for maximum performance data protection mode and is the default.</p> <a name="1017257"></a > <p class="BP">The effects of latency on primary throughput are detailed in the following white paper.</p> <a name="1009645"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layo ut table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="10096 49"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1009650"></a> <p class="NB"> "Oracle9<em class="Italic">i</em> Data Guard: Primary Site and Network Configuration Best Practices" at <code><a href="http://otn.ora cle.com/deploy/availability/htdocs/maa.htm">http://otn.oracle.com/deploy/availability/htdocs/maa.htm</a></code> for details about <co de>ARCH</code> performance and latency</p></td></tr></table></div> <a name="1007351"></a>  <h3 class="H2"><fon t face="Arial, Helvetica, sans-serif" color="#330099">Use the ASYNC Attribute with a 50 MB Buffer for Maximum Performance Mode</font> </h3>  <a name="1007352"></a> <p class="BP">The largest <code>LGWR ASYNC</code> buffer of 50 MB (<code>ASYNC=102400</c ode>) performs best in a WAN. In LAN tests, different asynchronous buffer sizes did not impact the primary database throughput. Using the maximum buffer size also increases the chance of avoiding timeout messages that result from an "async buffer full" condition in a WAN.</p> <a name="1007353"></a> <p class="BP">If the network buffer becomes full and remains full for 5 seconds, then the transpor t times out and converts to the <code>ARCH</code> transport. This condition indicates that the network to the standby destination can not keep up with the redo generation rate on the primary database. This indicated in the alert log by the following message:</p> <pre class="CE"><a name="1007354"></a>'Timing out on NetServer %d prod=%d,cons=%d,threshold=%d" <a name="1009694"></a> </pre> <a name="1 007355"></a> <p class="BP">This message indicates that the standby destination configured with the <code>LGWR ASYNC</code> attributes encountered an "async buffer full" condition. When this occurs, log transport services automatically stop using the network server p rocess to transmit the redo data and convert to using the archiver process (<code>ARC</code><em><code>n</code></em>) until a log swit ch occurs. The next log transmission reverts to the <code>ASYNC</code> transport. This change occurs automatically. Using the largest asynchronous network buffer, 30MB, increases the chance of avoiding the transport converting to <code>ARCH</code> and potentially lo sing more data.</p> <a name="1007356"></a> <p class="BP"><a href="configbp.htm#1009685">Figure 7-2</a> shows the architecture w hen the standby protection mode is set to maximum performance with <code>LGWR ASYNC</code> configuration. The <code>LGWR</code> reque st is buffered if sufficient space is available in the network buffer. If the production database fails and is inaccessible, then the data in the network buffer is lost, which usually means seconds of data loss in high OLTP applications.</p> <a name="1009685"></a> <h4 class="FT"><font face="Arial, Helvetica, sans-serif"><em>Figure 7-2 LGWR ASYNC Transport Service</em></font></h4> <a name="100968 6"><img src="maxav006.gif" alt="Text description of maxav006.gif follows"></a> <p><a href="img_text/maxav006.htm">Text description o f the illustration maxav006.gif</a></p> <a name="1007361"></a>  <h3 class="H2"><font face="Arial, Helvetica, s ans-serif" color="#330099">Evaluate SSH Port Forwarding with Compression</font></h3>  <a name="1013602"></a> <p class= "BP">Evaluate SSH port forwarding with compression for maximum performance mode over a high-latency WAN (RTT greater than 100 millise conds). Coupled with using <code>LGWR ASYNC</code>, the maximum buffer size, SSH with compression reduces the chance of receiving an "async buffer full" timeout. It also reduces network traffic.</p> <a name="1009748"></a> <div align="center"> <table class="NoteAlso " border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1009751"></a><font face="Arial, Helvetica, sans- serif"><strong class="NH">See Also:</strong></font> <a name="1009752"></a> <ul class="NL"> <li class="NL" type="disc"><a name="10097 53"></a>"Oracle9<em class="Italic">i</em> Data Guard: Primary Site and Network Configuration Best Practices" at <code><a href="http:/ /otn.oracle.com/deploy/availability/htdocs/maa.htm">http://otn.oracle.com/deploy/availability/htdocs/maa.htm</a></code></li> <li clas s="NL" type="disc"><a name="1009754"></a>MetaLink Note 225633.1 at <code><a href="http://metalink.oracle.com">http://metalink.oracle. com</a></code></li></ul></td></tr></table></div> <a name="1013801"></a>  <h3 class="H2"><font face="Arial, Hel vetica, sans-serif" color="#330099">Set LOG_ARCHIVE_LOCAL_FIRST to TRUE</font></h3>  <a name="1013802"></a> <p class=" BP">Setting <code>LOG_ARCHIVE_LOCAL_FIRST</code> to <code>TRUE</code> enables the archiver processes to archive the local online redo log files on the primary database before transmitting the redo data to remote standby destinations. This is especially useful when t he network to the standby databases is slow.</p> <a name="1016134"></a> <p class="BP">This is the default setting for <code>LOG_ARCH IVE_LOCAL_FIRST</code>.</p> <a name="1014587"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" c olor="#330099">Provide Secure Transmission of Redo Data</font></h3>  <a name="1014590"></a> <p class="BP">Because a la ck of security can directly affect availability, Data Guard provides a secure environment and prevents tampering with redo data as it is being transferred to the standby database. To enable secure transmission of redo data, set up every database in the Data Guard co nfiguration to use a password file, and set the password for the <code>SYS</code> user identically on every system. The following is a summary of steps needed for each database in the Data Guard configuration:</p> <ol class="LN1" type="1"> <li class="LN1" type="1" v alue="1"><a name="1014594"></a>Create a password file for each database in the Data Guard configuration.</li> <li class="LN1" type="1 " value="2"><a name="1014595"></a>Set the <code>REMOTE_LOGIN_PASSWORDFILE=[EXCLUSIVE | SHARED]</code> initialization parameter on eac h instance.</li></ol> <a name="1014596"></a> <p class="BP">After you have performed these steps to set up security on every database in the Data Guard configuration, Data Guard transmits redo data only after the appropriate authentication checks using <code>SYS</co de> credentials are successful. This authentication can be performed even if Oracle Advanced Security is not installed and provides s ome level of security when shipping redo data. To further protect redo data (for example, to encrypt redo data or to compute an integ rity checksum value for redo traffic over the network to disallow redo tampering on the network), Oracle recommends that you install and use Oracle Advanced Security.</p> <a name="1014626"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cel lpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a no te"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1014629"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">Se e Also:</strong></font> <a name="1014630"></a> <ul class="NL"> <li class="NL" type="disc"><a name="1014645"></a><em class="Italic">< a class="olinkSRC SBYDB" href="../../server$101/b10823/toc.htm">Oracle Data Guard Concepts and Administration</a></em> for detailed s teps for providing secure transmission of redo data</li> <li class="NL" type="disc"><a name="1014651"></a><em class="Italic"><a class ="olinkSRC ASOAG" href="../../network$101/b10772/toc.htm">Oracle Advanced Security Administrator's Guide</a></em></li></ul></td></tr> </table></div> <a name="1016594"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099 ">Set DB_UNIQUE_NAME</font></h3>  <a name="1016595"></a> <p class="BP">Specify a unique name for the standby database. The name does not change even if the primary and standby databases reverse roles. The <code>DB_UNIQUE_NAME</code> parameter defaults to the value of the <code>DB_NAME</code> parameter.</p> <a name="1016606"></a> <div align="center"> <table class="NoteAlso" border= "0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout t able to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1016613"></a><font face="Arial, Helvetica, sans-serif"><s trong class="NH">See Also:</strong></font> <a name="1016614"></a> <p class="NB"><em class="Italic"><a class="olinkSRC SBYDB" href=". ./../server$101/b10823/toc.htm">Oracle Data Guard Concepts and Administration</a></em></p></td></tr></table></div> <a name="1016596"> </a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Set LOG_ARCHIVE_CONFIG Correctl y</font></h3>  <a name="1016597"></a> <p class="BP">Specify the <code>DG_CONFIG</code> attribute of the <code>LOG_ARCH IVE_CONFIG</code> initialization parameter so that it lists the <code>DB_UNIQUE_NAME</code> for the primary database and each standby database in the Data Guard configuration. By default, this parameter enables the primary database to send redo data to remote destin ations and enables standby databases to receive redo data. The <code>DG_CONFIG</code> attribute must be set to enable the dynamic add ition of a standby database to a Data Guard configuration that has a RAC primary database running in either maximum protection or max imum availability mode.</p> <a name="1016610"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding=" 0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr c lass="NoteAlso"> <td class="NoteAlso"><a name="1016623"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</s trong></font> <a name="1016629"></a> <p class="NB"><em class="Italic"><a class="olinkSRC SBYDB" href="../../server$101/b10823/toc.ht m">Oracle Data Guard Concepts and Administration</a></em></p></td></tr></table></div> <a name="1013803"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Recommendations for the Physical Standby Database Only</font ></h3>  <a name="1013808"></a> <p class="BP">The following recommendation applies only to the physical standby databas e:</p> <ul class="LB1"> <li class="LB1" type="disc"><a name="1013809"></a><a href="configbp.htm#1007363">Tune Media Recovery Performa nce</a></li></ul> <a name="1007363"></a>  <h4 class="H3"><font face="Arial, Helvetica, sans-serif" color="#330 099">Tune Media Recovery Performance</font></h4>  <a name="1007364"></a> <p class="BP">To use Oracle Data Guard with a physical standby database or to use any media recovery operation effectively, you need to tune your database recovery.</p> <a name=" 1009784"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary= "This is a layout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso" ><a name="1009790"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1009791"></a> <p class="NB">"Oracle9<em class="Italic">i</em> Media Recovery Best Practices" at <code><a href="http://otn.oracle.com/deploy/availa bility/htdocs/maa.htm">http://otn.oracle.com/deploy/availability/htdocs/maa.htm</a></code></p></td></tr></table></div> <a name="10138 23"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Recommendations for the Log ical Standby Database Only</font></h3>  <a name="1013868"></a> <p class="BP">The following recommendations apply only to the logical standby database:</p> <ul class="LB1"> <li class="LB1" type="disc"><a name="1013869"></a><a href="configbp.htm#1013958 ">Use Supplemental Logging and Primary Key Constraints</a></li> <li class="LB1" type="disc"><a name="1013895"></a><a href="configbp.h tm#1013872">Set the MAX_SERVERS Initialization Parameter</a></li> <li class="LB1" type="disc"><a name="1013900"></a><a href="configbp .htm#1013997">Increase the PARALLEL_MAX_SERVERS Initialization Parameter</a></li> <li class="LB1" type="disc"><a name="1013910"></a>< a href="configbp.htm#1013878">Set the TRANSACTION_CONSISTENCY Initialization Parameter</a></li> <li class="LB1" type="disc"><a name=" 1013915"></a><a href="configbp.htm#1013880">Skip SQL Apply for Unnecessary Objects</a></li></ul> <a name="1013958"></a>  <h4 class="H3"><font face="Arial, Helvetica, sans-serif" color="#330099">Use Supplemental Logging and Primary Key Constrai nts</font></h4>  <a name="1017273"></a> <p class="BP">Use supplemental logging and primary key constraints on all prod uction tables.</p> <a name="1017305"></a> <p class="BP">If your application ensures that the rows in a table are unique, then you ca n create a disabled primary key <code>RELY</code> constraint on the table. This avoids the overhead of maintaining a primary key on t he primary database. To create a disabled <code>RELY</code> constraint on a primary database table, use the <code>ALTER TABLE</code> statement with a <code>RELY DISABLE</code> clause.</p> <a name="1017289"></a> <p class="BP">To improve the performance of SQL Apply, add an index to the columns that uniquely identify the row on the logical standby database. Failure to do this results in full table scans.</p> <a name="1013872"></a>  <h4 class="H3"><font face="Arial, Helvetica, sans-serif" color="#330099">S et the MAX_SERVERS Initialization Parameter</font></h4>  <a name="1013969"></a> <p class="BP">If the logical standby d atabase is being used to remove reporting or decision support operations from the primary database, then you should probably reserve some of the parallel query slaves for such operations. Because the SQL Apply process by default uses all the parallel query slaves, s etting the <code>MAX_SERVERS</code> initialization parameter enables a specified number of parallel query slaves to be reserved.</p> <a name="1013999"></a> <p class="BP"><a href="configbp.htm#1014003">Table 7-5</a> shows examples of <code>MAX_SERVERS</code> va lues.</p> <a name="1014000"></a> <h5 class="TTW"><a name="1014000"></a><a name="1014003"></a> <strong><font face="Arial, Helvetica, sans-serif"><em>Table 7-5 Examples of MAX_SERVERS Values </em></font></strong></h5> <table summary="" class="HRuleFormalWide" b order="1" frame="HSIDES" rules="ROWS" width="100%" cellpadding="3" cellspacing="0" dir="ltr" title=""> <thead> <tr class="Formal"> <t h class="Formal" align="left" valign="bottom" scope="col"><a name="1014007"></a> <font face="Arial, Helvetica, sans-serif"><strong>PA RALLEL_MAX_SERVERS Initialization Parameter</strong></font></th> <th class="Formal" align="left" valign="bottom" scope="col"><a name= "1014009"></a> <font face="Arial, Helvetica, sans-serif"><strong>MAX_SERVERS Initialization Parameter</strong></font></th> <th class= "Formal" align="left" valign="bottom" scope="col"><a name="1014037"></a> <font face="Arial, Helvetica, sans-serif"><strong>Number of Servers Reserved for Parallel Query Operations</strong></font></th> <th class="Formal" align="left" valign="bottom" scope="col"><a na me="1014039"></a> <font face="Arial, Helvetica, sans-serif"><strong>Number of Servers Reserved for SQL Apply Operations</strong></fon t></th></tr></thead> <tbody> <tr class="Formal" align="left" valign="top"> <td class="Formal"><a name="1014011"></a> <p class="TB">2 4</p></td> <td class="Formal"><a name="1014013"></a> <p class="TB">Unset</p></td> <td class="Formal"><a name="1014041"></a> <p clas s="TB">0</p></td> <td class="Formal"><a name="1014043"></a> <p class="TB">24</p></td></tr> <tr class="Formal" align="left" valign="t op"> <td class="Formal"><a name="1014015"></a> <p class="TB">24</p></td> <td class="Formal"><a name="1014017"></a> <p class="TB">24 </p></td> <td class="Formal"><a name="1014045"></a> <p class="TB">0</p></td> <td class="Formal"><a name="1014047"></a> <p class="TB ">24</p></td></tr> <tr class="Formal" align="left" valign="top"> <td class="Formal"><a name="1014019"></a> <p class="TB">48</p></td> <td class="Formal"><a name="1014021"></a> <p class="TB">24</p></td> <td class="Formal"><a name="1014049"></a> <p class="TB">24</p> </td> <td class="Formal"><a name="1014051"></a> <p class="TB">24</p></td></tr></tbody></table> <a name="1014060"></a> <p class="BP" >It is recommended that <code>MAX_SERVERS</code> be set initially to the larger of the following values: 9 or 3 plus 3 times CPU.</p> <a name="1013997"></a>  <h4 class="H3"><font face="Arial, Helvetica, sans-serif" color="#330099">Increase the PARALLEL_MAX_SERVERS Initialization Parameter</font></h4>  <a name="1014062"></a> <p class="BP">Increase the <code>PA RALLEL_MAX_SERVERS</code> initialization parameter by the larger of 9 or 3 times CPU on both the primary and standby instances:</p> < pre class="CE"><a name="1014073"></a>PARALLEL_MAX_SERVERS=current value + max(9, 3 +(3 x CPU)) <a name="1014074"></a> </pre> <a name ="1014063"></a> <p class="BP">The <code>PARALLEL_MAX_SERVERS</code> initialization parameter specifies the maximum number of parallel query processes that can be created on the database instance. With the exception of the coordinator process, all the processes that constitute the SQL Apply engine are created from the pool of parallel query processes. The SQL Apply engine, by default, uses all the parallel query processes available on the database instance. This behavior can be overridden by using the logical standby parameters </p> <a name="1014064"></a> <p class="BP">It is recommended that <code>PARALLEL_MAX_SERVERS</code> be increased by the value of <cod e>MAX_SERVERS</code>.</p> <a name="1013878"></a>  <h4 class="H3"><font face="Arial, Helvetica, sans-serif" col or="#330099">Set the TRANSACTION_CONSISTENCY Initialization Parameter</font></h4>  <a name="1014104"></a> <p class="BP ">The logical standby database supports the following methods of data application:</p> <ul class="LB1"> <li class="LB1" type="disc">< a name="1014105"></a>For a reporting or decision support system, use <code>FULL</code> or <code>READ_ONLY</code> transaction consiste ncy.</li> <li class="LB1" type="disc"><a name="1014106"></a>For a disaster recovery solution or when the SQL Apply engine needs to ca tch up, set <code>TRANSACTION_CONSISTENCY</code> to <code>NONE</code>.</li></ul> <a name="1014107"></a> <p class="BP">If the logical standby database will be used for reporting or decision support operations, then:</p> <ul class="LB1"> <li class="LB1" type="disc">< a name="1014108"></a>If the standby database has multiple instances (RAC), then choose <code>FULL</code>.</li> <li class="LB1" type=" disc"><a name="1014109"></a>If the standby database has only one instance (no RAC), then choose <code>READ_ONLY</code>.</li></ul> <a name="1013880"></a>  <h4 class="H3"><font face="Arial, Helvetica, sans-serif" color="#330099">Skip SQL Apply f or Unnecessary Objects</font></h4>  <a name="1014146"></a> <p class="BP">Database objects that do not need to be repli cated to the standby database should be skipped by using the <code>DBMS_LOGSTDBY.SKIP</code> procedure. Skipping such objects reduces the processing of the the SQL Apply engine. Consider this recommendation in a decision support environment.</p> <a name="1013204"></ a>  <h2 class="H1"><font face="Arial, Helvetica, sans-serif" color="#330099">Configuration Best Practices for MAA</font></h2>  <a name="1013207"></a> <p class="BP">This section recommends configuration practices in addition to t he ones that are discussed for the single-instance database, RAC, and Data Guard. These practices are recommended when MAA is employe d (RAC and Data Guard are used on both sites).</p> <a name="1014221"></a> <p class="BP">This section includes the following topics:< /p> <ul class="LB1"> <li class="LB1" type="disc"><a name="1013209"></a><a href="configbp.htm#1013211">Configure Multiple Standby Inst ances</a></li> <li class="LB1" type="disc"><a name="1014222"></a><a href="configbp.htm#1014224">Configure Connect-Time Failover for N etwork Service Descriptors</a></li></ul> <a name="1013211"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Configure Multiple Standby Instances</font></h3>  <a name="1013244"></a> <p class="BP">In an MAA environment, the standby database uses RAC, and multiple standby instances are associated with the same standby database. Havi ng multiple standby instances is not the same as having multiple standby databases. Only one instance can have the managed recovery p rocess (MRP) or the logical standby apply process (LSP). The standby instance with the MRP or LSP is called the primary standby insta nce. All other standby instances are called secondary standby instances.</p> <a name="1013212"></a> <p class="BP">Having multiple st andby instances for the same database on the cluster provides the following benefits:</p> <ul class="LB1"> <li class="LB1" type="disc "><a name="1013213"></a>They enable transparent connection failover to a secondary standby instance if connectivity to the primary st andby instance fails. In this scenario, the MRP or LSP session is automatically restarted by the Data Guard Broker. If the Broker is not being used, then these processes must be restarted manually on the new primary standby instance.</li> <li class="LB1" type="disc" ><a name="1013216"></a>They provide a scheduled maintenance solution whenever the primary standby instance and host need to be shut d own for maintenance. The secondary standby can take over and receive logs through Oracle Net service because connect-time failover oc curs.</li></ul> <a name="1014224"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#33009 9">Configure Connect-Time Failover for Network Service Descriptors</font></h3>  <a name="1014225"></a> <p class="BP">D ata Guard connect-time failover occurs when a connection request is forwarded to another listener if the connection fails. Connect-ti me failover is enabled by service registration, because the listener knows which available Oracle instance provides the requested ser vice.</p> <a name="1014998"></a> <p class="BP">The following is an Oracle Net connection descriptor in the <code>tnsnames.ora</code> file:</p> <pre class="CE"><a name="1014989"></a>sales.us.acme.com= <a name="1014990"></a> (DESCRIPTION= <a name="1014991"></a> (ADD RESS_LIST= <a name="1014992"></a> (ADDRESS=(PROTOCOL=tcp)(HOST=sales1-server)(PORT=1521)) <a name="1014993"></a> (ADDRESS=(PROT OCOL=tcp)(HOST=sales2-server)(PORT=1521))) <a name="1014994"></a> (CONNECT_DATA= <a name="1014995"></a> (SERVICE_NAME=sales.us.ac me.com))) <a name="1014987"></a> </pre> <a name="1014986"></a> <p class="BP">Note that the <code>SALES</code> net service name conta ins multiple address lists (two because it is a two-node cluster) for the production and standby clusters. The second address list en ables connect-time failover if the first connection fails. This works for all protection modes.</p> <a name="1014999"></a> <p class= "BP">To add a network protocol address to an existing net service name or database service, use either Oracle Enterprise Manager or O racle Net Manager.</p> <a name="1015000"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" ce llspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class= "NoteAlso"> <td class="NoteAlso"><a name="1015003"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong ></font> <a name="1015004"></a> <p class="NB"><em class="Italic"><a class="olinkSRC NETAG" href="../../network$101/b10775/toc.htm">O racle Net Services Administrator's Guide</a></em></p></td></tr></table></div> <a name="1007375"></a>  <h2 clas s="H1"><font face="Arial, Helvetica, sans-serif" color="#330099">Recommendations for Backup and Recovery</font></h2>  < a name="1007376"></a> <p class="BP">While it is prudent that every database have a good backup, recovery using a backup is not alway s the fastest solution. Other available Oracle technologies, such as RAC, Data Guard, and flashback technology often provide faster m eans of recovering from an outage than restoring from backups.</p> <a name="1007379"></a> <p class="BP">A good backup and recovery s trategy is still vital to the overall high availability solution and ensures that specific outages are recovered from in an acceptabl e amount of time. The following topics are included in this section:</p> <dl class="LS"> <dt class="LSF"><a name="1007381"></a><a hre f="configbp.htm#1016687">Use Recovery Manager to Back Up Database Files</a></dt> <dt class="LSF"><a name="1016647"></a><a href="confi gbp.htm#1007392">Understand When to Use Backups</a></dt> <dt class="LSF"><a name="1016648"></a><a href="configbp.htm#1007415">Use an RMAN Recovery Catalog</a></dt> <dt class="LSF"><a name="1016815"></a><a href="configbp.htm#1016773">Use the Autobackup Feature for th e Control File and SPFILE</a></dt> <dt class="LSF"><a name="1016820"></a><a href="configbp.htm#1016775">Use Incrementally Updated Bac kups to Reduce Restoration Time</a></dt> <dt class="LSF"><a name="1016825"></a><a href="configbp.htm#1016777">Enable Change Tracking to Reduce Backup Time</a></dt> <dt class="LSF"><a name="1016830"></a><a href="configbp.htm#1016779">Create Database Backups on Disk i n the Flash Recovery Area</a></dt> <dt class="LSF"><a name="1016835"></a><a href="configbp.htm#1016781">Create Tape Backups from the Flash Recovery Area</a></dt> <dt class="LSF"><a name="1016840"></a><a href="configbp.htm#1016794">Determine Retention Policy and Back up Frequency</a></dt> <dt class="LSF"><a name="1016845"></a><a href="configbp.htm#1016801">Configure the Size of the Flash Recovery A rea Properly</a></dt> <dt class="LSF"><a name="1016850"></a><a href="configbp.htm#1016783">In a Data Guard Environment, Back Up to th e Flash Recovery Area on All Sites</a></dt> <dt class="LSF"><a name="1016855"></a><a href="configbp.htm#1007453">During Backups, Use the Target Database Control File as the RMAN Repository</a></dt> <dt class="LSF"><a name="1016859"></a><a href="configbp.htm#1016805" >Regularly Check Database Files for Corruption</a></dt> <dt class="LSF"><a name="1016868"></a><a href="configbp.htm#1007459">Periodic ally Test Recovery Procedures</a></dt> <dt class="LSF"><a name="1016872"></a><a href="configbp.htm#1016807">Back Up the OCR to Tape o r Offsite</a> <a name="1013307"></a></dt> <dd> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" ce llspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class= "NoteAlso"> <td class="NoteAlso"><a name="1013310"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong ></font> <a name="1013311"></a> <ul class="NL"> <li class="NL" type="disc"><a name="1016666"></a><em class="Italic"><a class="olinkS RC BRBSC" href="../../server$101/b10735/toc.htm">Oracle Database Backup and Recovery Basics</a></em></li> <li class="NL" type="disc"> <a name="1016665"></a><em class="Italic"><a class="olinkSRC BRADV" href="../../server$101/b10734/toc.htm">Oracle Database Backup and Recovery Advanced User's Guide</a></em> for more information about backup and recovery topics, including RMAN</li></ul></td></tr></ta ble></div></dd></dl> <a name="1016687"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="# 330099">Use Recovery Manager to Back Up Database Files</font></h3>  <a name="1016688"></a> <p class="BP">Recovery Mana ger (RMAN) uses server sessions to perform backup and recovery operations and stores metadata about backups in a repository. RMAN off ers many advantages over typical user-managed backup methods, such as the ability to do online database backups without placing table spaces in backup mode; support for incremental backups; data block integrity checks during backup and restore operations; and the abi lity to test backups and restores without actually performing the operation. RMAN automates backup and recovery, whereas the user-man aged method requires you to keep track of all database files and backups. For example, instead of requiring you to locate backups for each datafile, copy them to the correct place using operating system commands, and choose which logs to apply; RMAN manages these ta sks automatically. There are also capabilities of Oracle recovery that are only available when using RMAN, such as block media recove ry.</p> <a name="1007392"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Under stand When to Use Backups</font></h3>  <a name="1016682"></a> <p class="BP">Most production database unscheduled outag es are either handled automatically by various database components or are resolved by using another technology to restore a backup. F or example, some outages are handled best by using Flashback Database or the standby database. However, there are situations that req uire using database backups, including the following:</p> <ul class="LB1"> <li class="LB1" type="disc"><a name="1007398"></a><a href= "configbp.htm#1007405">Perform Regular Backups</a></li> <li class="LB1" type="disc"><a name="1017309"></a><a href="configbp.htm#10173 10">Initial Data Guard Environment Set-Up</a></li> <li class="LB1" type="disc"><a name="1016709"></a><a href="configbp.htm#1016710">R ecovering from Data Failures Using File or Block Media Recovery</a></li> <li class="LB1" type="disc"><a name="1007399"></a><a href="c onfigbp.htm#1007407">Double Failure Resolution</a></li> <li class="LB1" type="disc"><a name="1007400"></a><a href="configbp.htm#10074 09">Long-Term Backups</a></li></ul> <a name="1007405"></a>  <h4 class="H3"><font face="Arial, Helvetica, sans- serif" color="#330099">Perform Regular Backups</font></h4>  <a name="1017311"></a> <p class="BP">Perform regular backu ps.</p> <a name="1017312"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" d ir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1017315"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a nam e="1017316"></a> <p class="NB"><a href="configbp.htm#1016794">"Determine Retention Policy and Backup Frequency"</a><a href="configbp .htm#1016794"></a></p></td></tr></table></div> <a name="1017310"></a>  <h4 class="H3"><font face="Arial, Helve tica, sans-serif" color="#330099">Initial Data Guard Environment Set-Up</font></h4>  <a name="1016712"></a> <p class=" BP">During initial set-up of a standby database, a backup of the production database is required at the secondary site to create the initial standby database.</p> <a name="1016717"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding ="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1016720"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:< /strong></font> <a name="1016721"></a> <p class="NB"><em class="Italic"><a class="xlinkSRC SBYDB00210" href="../../server$101/b10823 /create_ps.htm#SBYDB00210">Oracle Data Guard Concepts and Administration</a></em></p></td></tr></table></div> <a name="1016710"></a>  <h4 class="H3"><font face="Arial, Helvetica, sans-serif" color="#330099">Recovering from Data Failures Using File or Block Media Recovery</font></h4>  <a name="1007406"></a> <p class="BP">When a data failure, which includes blo ck corruption and media failure, occurs in an environment that does not include Data Guard, the only method of recovery is using an e xisting backup. Even with Data Guard, the most efficient means of recovering from data failure may be restoring and recovering the af fected object from an existing backup.</p> <a name="1016730"></a> <div align="center"> <table class="NoteAlso" border="0" width="80% " cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1016733"></a><font face="Arial, Helvetica, sans-serif"><strong class="N H">See Also:</strong></font> <a name="1016734"></a> <p class="NB"><a href="recover.htm#1010991">"Recovery Methods for Data Failures" </a><a href="recover.htm#1010991"></a></p></td></tr></table></div> <a name="1007407"></a>  <h4 class="H3"><fon t face="Arial, Helvetica, sans-serif" color="#330099">Double Failure Resolution</font></h4>  <a name="1007408"></a> <p class="BP">A double failure scenario affects the availability of both the production and standby databases. The only resolution of t his situation is to re-create the production database from an available backup, then re-create the standby database. An example of a double failure scenario is a site outage at the secondary site, which eliminates fault tolerance, followed by a media failure on the production database. Some multiple failures, or more appropriately disasters (such as a primary site outage followed by a secondary s ite outage) may require the use of backups that exist in an offsite location, so developing and following a process to deliver and ma intain backup tapes at an offsite location is necessary to restore service in the most dire of circumstances.</p> <a name="1007409">< /a>  <h4 class="H3"><font face="Arial, Helvetica, sans-serif" color="#330099">Long-Term Backups</font></h4> <! --/TOC=h3--> <a name="1007410"></a> <p class="BP">Some businesses require the ability to maintain long-term backups that may be need ed years into the future. By using RMAN with the <code>KEEP</code> option, it is possible to retain backups that are exempt from the retention policy and never expire, providing the capability to restore and recover the database to any desired point in time. It is i mportant that a recovery catalog be used for the RMAN repository so that backup metadata is not lost due to lack of space, which may occur when using the target database control file for the RMAN repository.</p> <a name="1007415"></a>  <h3 cla ss="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Use an RMAN Recovery Catalog</font></h3>  <a name="10 07416"></a> <p class="BP">RMAN automatically manages the backup metadata in the control file of the database that is being backed up . To protect and keep backup metadata for long periods of time, the RMAN repository, usually referred to as a recovery catalog, is cr eated in a separate database. There are many advantages of using a recovery catalog, including the ability to store backup informatio n long-term, the ability to store metadata for multiple databases, and the ability to restore an available backup on to another syste m. In addition, if you are using only the target database control file to house the repository, the control file, with its limited ma ximum size, may not be large enough to hold all desired backup metadata. If the control file is too small to hold additional backup m etadata, then existing backup information is overwritten, making it difficult to restore and recover using those backups.</p> <a name ="1016773"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Use the Autobackup F eature for the Control File and SPFILE</font></h3>  <a name="1016774"></a> <p class="BP">RMAN can be configured to aut omatically back up the control file and server parameter file (<code>SPFILE</code>) whenever the database structure metadata in the c ontrol file changes and whenever a backup record is added. The autobackup enables RMAN to recover the database even if the current co ntrol file, catalog, and <code>SPFILE</code> are lost. The RMAN autobackup feature is enabled with the <code>CONFIGURE CONTROLFILE AU TOBACKUP ON</code> statement.</p> <a name="1016775"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-se rif" color="#330099">Use Incrementally Updated Backups to Reduce Restoration Time</font></h3>  <a name="1016776"></a> <p class="BP">Oracle's incrementally updated backups feature enables you to create an image copy of a datafile, then regularly create incremental backups of the database and apply them to that image copy. The image copy is updated with all changes up through the SCN at which the incremental backup was taken. RMAN can use the resulting updated datafile in media recovery just as it would use a full image copy taken at that SCN, without the overhead of performing a full image copy of the database every day. A backup strategy base d on incrementally updated backups can help minimize MTTR for media recovery.</p> <a name="1016886"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1016889"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1016890"></a> <p class="NB"><em class="Italic"><a class ="olinkSRC BRBSC" href="../../server$101/b10735/toc.htm">Oracle Database Backup and Recovery Basics</a></em></p></td></tr></table></d iv> <a name="1016777"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Enable Ch ange Tracking to Reduce Backup Time</font></h3>  <a name="1016778"></a> <p class="BP">Oracle's change tracking feature for incremental backups improves incremental backup performance by recording changed blocks in each datafile in a change tracking fi le. If change tracking is enabled, then RMAN uses the change tracking file to identify changed blocks for incremental backup, thus av oiding the need to scan every block in the datafile.</p> <a name="1016896"></a> <div align="center"> <table class="NoteAlso" border= "0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout t able to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1016900"></a><font face="Arial, Helvetica, sans-serif"><s trong class="NH">See Also:</strong></font> <a name="1016906"></a> <p class="NB"><em class="Italic"><a class="olinkSRC BRBSC" href=". ./../server$101/b10735/toc.htm">Oracle Database Backup and Recovery Basics</a></em></p></td></tr></table></div> <a name="1016779"></a >  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Create Database Backups on Disk in the Flash Recovery Area</font></h3>  <a name="1016780"></a> <p class="BP">Using automatic disk-based backup and recov ery, you can create a flash recovery area, which automates management of backup-related files. Choose a location on disk and an upper bound for storage space and set a retention policy that governs how long backup files are needed for recovery. Oracle manages the st orage used for backup, archived redo logs, and other recovery-related files for your database within that space. Files no longer need ed are eligible for deletion when RMAN needs to reclaim space for new files.</p> <a name="1016910"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" t itle="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1016914"></a><font face="Arial, H elvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1016920"></a> <p class="NB"><em class="Italic"><a class= "olinkSRC BRBSC" href="../../server$101/b10735/toc.htm">Oracle Database Backup and Recovery Basics</a></em></p></td></tr></table></di v> <a name="1016781"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Create Tap e Backups from the Flash Recovery Area</font></h3>  <a name="1016782"></a> <p class="BP">Use the <code>BACKUP RECOVERY FILE DESTINATION</code> RMAN command to move disk backups created in the flash recovery area to tape. Tape backups are used for offs ite and long-term storage and are used to handle certain outage scenarios.</p> <a name="1016924"></a> <div align="center"> <table cl ass="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" tit le="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1016928"></a><font face="Arial, Hel vetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1016934"></a> <p class="NB"><em class="Italic"><a class="o linkSRC BRBSC" href="../../server$101/b10735/toc.htm">Oracle Database Backup and Recovery Basics</a></em></p></td></tr></table></div> <a name="1016794"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Determine Re tention Policy and Backup Frequency</font></h3>  <a name="1016795"></a> <p class="BP">The backup retention policy is t he rule set regarding which backups must be retained (on disk or other backup media) to meet recovery and other requirements. It may be safe to delete a specific backup because it is old enough to be superseded by more recent backups or because it has been stored on tape. You may also need to retain a specific backup on disk for other reasons such as archival requirements. A backup that is no lon ger needed to satisfy the backup retention policy is said to be <strong class="Bold">obsolete</strong>.</p> <a name="1017328"></a> < p class="BP">Backup retention policy can be based on <strong class="Bold">redundancy</strong> or a <strong class="Bold">recovery wind ow</strong>. In a redundancy-based retention policy, you specify a number <em class="Italic">n</em> such that you always keep at leas t <em class="Italic">n</em> distinct backups of each file in your database. In a recovery window-based retention policy, you specify a time interval in the past (for example, one week or one month) and keep all backups required to let you perform point-in-time recov ery to any point during that window.</p> <a name="1017329"></a> <p class="BP">Frequent backups are essential for any recovery scheme . Base the frequency of backups on the rate or frequency of database changes such as:</p> <ul class="LB1"> <li class="LB1" type="disc "><a name="1017330"></a>Addition and deletion of tables</li> <li class="LB1" type="disc"><a name="1017331"></a>Insertions and deletio ns of rows in existing tables</li> <li class="LB1" type="disc"><a name="1017332"></a>Updates to data within tables</li></ul> <a name= "1017333"></a> <p class="BP">The more frequently your database is updated, the more often you should perform database backups. If da tabase updates are relatively infrequent, then you can make whole database backups infrequently and supplement them with incremental backups, which will be relatively small because few blocks have changed.</p> <a name="1017334"></a> <div align="center"> <table clas s="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title ="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1017337"></a><font face="Arial, Helve tica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1017338"></a> <p class="NB"><em class="Italic"><a class="oli nkSRC BRBSC" href="../../server$101/b10735/toc.htm">Oracle Database Backup and Recovery Basics</a></em></p></td></tr></table></div> < a name="1016801"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Configure the Size of the Flash Recovery Area Properly</font></h3>  <a name="1016802"></a> <p class="BP">Configuring the size of the flash recovery area properly enables fast recovery from user error with Flashback Database and fast recovery from data failure with file or block media recovery from disk. The appropriate size of the flash recovery area depends on the following: retention policy, b ackup frequency, size of the database, rate and number of changes to the database. Specific formulas for determining the proper size of the flash recovery area for different backup scenarios are provided in <em class="Italic"><a class="olinkSRC BRBSC" href="../../se rver$101/b10735/toc.htm">Oracle Database Backup and Recovery Basics</a>.</em></p> <a name="1016783"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">In a Data Guard Environment, Back Up to the Flash Recovery Area on All Sites</font></h3>  <a name="1016784"></a> <p class="BP">Take backups at the primary and secondary sites. The ad vantages of this practice are as follows:</p> <ul class="LB1"> <li class="LB1" type="disc"><a name="1016949"></a>It significantly red uces MTTR in certain double outage scenarios.</li> <li class="LB1" type="disc"><a name="1016950"></a>It avoids introducing new backup procedures upon a switchover or failover.</li> <li class="LB1" type="disc"><a name="1016951"></a>RMAN file and block media recovery is a recovery option for data failure outages at both primary and secondary sites.</li></ul> <a name="1016952"></a> <p class="BP">Co nsider a scenario in which backups are done only at the secondary site. Suppose there is a site outage at the secondary site where th e estimated time to recover is three days. The primary site is completely vulnerable to an outage that is typically resolved by a fai lover, also to any outage that could be resolved by having a local backup (such as a data failure outage resolved by block media reco very). In this scenario, a production database outage can be resolved only by physically shipping the off-site tape backups that were taken at the standby site. If primary site backups were available, then restoring locally would be an available option in place of t he failover than cannot be done. Data may be lost, but having primary site backups significantly shortens the MTTR.</p> <a name="1016 953"></a> <p class="BP">Another undesirable approach is to start taking primary site backups at the time that there is a secondary s ite outage. However, this approach should be avoided because it is introducing new processes and procedures at a time when the enviro nment is already under duress and the impact of a mistake by staff will be magnified. Also, it is not a time to learn that backups ca nnot be taken at the primary site.</p> <a name="1016954"></a> <p class="BP">In addition, primary site disk backups are necessary to ensure a reasonable MTTR when using RMAN file or block media recovery. Without a local on-disk backup, a backup taken at the standby site must be restored to the primary site, significantly lengthening the MTTR for this type of outage.</p> <a name="1007453"></a> <!- -TOC=h2-"1007453"--> <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">During Backups, Use the Target Database Control File as the RMAN Repository</font></h3>  <a name="1010242"></a> <p class="BP">During backups, use the target database control file as the RMAN repository and resynchronize afterward with the RMAN <code>RESYNC CATALOG</code> command.</p> <a na me="1007454"></a> <p class="BP">When creating backups to disk or tape, use the target database control file as the RMAN repository s o that the ability to back up or the success of the backup does not depend on the availability of the RMAN catalog in the manageabili ty database. This is accomplished by running RMAN with the <code>NOCATALOG</code> option. After the backup is complete, the new backu p information stored in the target database control file can be resynchronized with the recovery catalog using the <code>RESYNC CATAL OG</code> command.</p> <a name="1016805"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color= "#330099">Regularly Check Database Files for Corruption</font></h3>  <a name="1016806"></a> <p class="BP">Using the <c ode>BACKUP VALIDATE</code> RMAN command, database files should be checked regularly for block corruptions that have not yet been repo rted by a user session or by normal backup operations. RMAN scans the specified files and verifies content-checking for physical and logical errors but does not actually perform the backup or recovery operation. Oracle records the address of the corrupt block and th e type of corruption in the control file. Access these records through the <code>V$DATABASE_BLOCK_CORRUPTION</code> view, which can b e used by RMAN block media recovery.</p> <a name="1016955"></a> <p class="BP">If <code>BLOCK CHANGE TRACKING</code> is enabled, then do not use the <code>INCREMENTAL LEVEL</code> option with <code>BACKUP VALIDATE</code> to ensure that all data blocks are read and v erified.</p> <a name="1016956"></a> <p class="BP">To detect all types of corruption that are possible to detect:</p> <ul class="LB1" > <li class="LB1" type="disc"><a name="1016957"></a>Do not specify the <code>MAXCORRUPT</code> option</li> <li class="LB1" type="disc "><a name="1016958"></a>Do not specify the <code>NOCHECKSUM</code> option</li> <li class="LB1" type="disc"><a name="1016959"></a>Do s pecify the <code>CHECK LOGICAL</code> option</li></ul> <a name="1007459"></a>  <h3 class="H2"><font face="Aria l, Helvetica, sans-serif" color="#330099">Periodically Test Recovery Procedures</font></h3>  <a name="1007460"></a> <p class="BP">Complete, successful, and tested backups are fundamental to the success of any recovery. Create test plans for the differ ent outage types. Start with the most common outage types and progress to the least probable. Issuing backup procedures does not ensu re that the backups are successful; they must be rehearsed. Monitor the backup procedure for errors, and validate backups by testing your recovery procedures periodically. Also, validate the ability to do backups and restores by using the RMAN commands <code>BACKUP VALIDATE</code> and <code>RESTORE... VALIDATE</code> commands.</p> <a name="1016960"></a> <div align="center"> <table class="NoteAls o" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1016964"></a><font face="Arial, Helvetica, sans -serif"><strong class="NH">See Also:</strong></font> <a name="1016970"></a> <p class="NB"><em class="Italic"><a class="olinkSRC BRBS C" href="../../server$101/b10735/toc.htm">Oracle Database Backup and Recovery Basics</a></em></p></td></tr></table></div> <a name="10 16807"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Back Up the OCR to Tape or Offsite</font></h3>  <a name="1016808"></a> <p class="BP">The Oracle Cluster Registry (OCR) contains cluster and da tabase configuration information for RAC and Cluster Ready Services (CRS), such as the cluster database node list, CRS application re source profiles, and Event Manager (EVM) authorizations. Using the <code>ocrconfig</code> tool, there are two methods of copying OCR content and using the content for recovery. The first method uses automatically generated physical OCR file copies. The second method uses manually created logical OCR export files. The backup file created with <code>ocrconfig</code> should be backed as part of the operating system backup using standard operating system or third-party tools.</p> <a name="1016978"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1016986"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1016987"></a> <p class="NB"><em class="Italic"><a class ="olinkSRC RACAD" href="../../rac$101/b10765/toc.htm">Oracle Real Application Clusters Administrator's Guide</a></em></p></td></tr></ table></div> <a name="1010806"></a>  <h2 class="H1"><font face="Arial, Helvetica, sans-serif" color="#330099"> Recommendations for Fast Application Failover</font></h2>  <a name="1015018"></a> <p class="BP">In any high availabili ty architecture, client and mid-tier applications can be redirected to available services within a Real Application Cluster and with some customization to a Data Guard or replicated database. This redirection can usually be transparent and can be used to reduce or e liminate both planned and unplanned downtime to the client or mid-tier application.</p> <a name="1015020"></a> <p class="BP">Service s are prerequisites for fast, transparent application failover. When you create services in RAC, you can assign the services to insta nces for preferred (normal) and available (recovery) processing. When an instance to which you have assigned a service becomes unavai lable, RAC can reconnect users connected to that instance to an available instance without service interruptions. Clients and mid-tie r applications make connection requests by specifying a service using a global name. The connection information must be aware of all potential production instances or databases that can publish that service. Services enable you to model and deploy both planned and u nplanned operations for any type of high availability or disaster recovery scenario.</p> <a name="1015022"></a> <p class="BP">To res pond to changes in the cluster database, RAC's Cluster Ready Services (CRS), event system, and service callouts can be used to notify clients and mid-tier applications automatically. Event notifications can be configured to initiate recovery processing after failure s to eliminate network timeouts and to provide end-to-end control over essential resources. These rapid notifications are done automa tically from RAC to JDBC clients through JDBC fast connection failover. However, RAC provides a robust callout and event system that enables the user to customize specialized callouts to respond to database <code>UP</code> and <code>DOWN</code> events. Use these cal louts to notify middle-tier applications to interrupt existing problematic connections and redirect new connections to available reso urces.</p> <a name="1015024"></a> <p class="BP">For disaster recovery, the new production database can also be configured to publish the production service while stopping the services on the old production database. Again, callouts are required to notify the mid-ti er applications.</p> <a name="1015029"></a> <p class="BP">To configure for fast application failover, follow these recommendations f or middle-tier applications and clients:</p> <ul class="LB1"> <li class="LB1" type="disc"><a name="1015032"></a><a href="configbp.htm #1015051">Configure Connection Descriptors for All Possible Production Instances</a></li> <li class="LB1" type="disc"><a name="101503 3"></a><a href="configbp.htm#1015094">Use RAC Availability Notifications and Events</a></li> <li class="LB1" type="disc"><a name="101 5034"></a><a href="configbp.htm#1015730">Use Transparent Application Failover If RAC Notification Is Not Feasible</a> <ul class="LD2 "> <li class="LD2" type="CIRCLE"><a name="1015035"></a>Use proper retries and delays to connect to the disaster recovery site</li> <l i class="LD2" type="CIRCLE"><a name="1015036"></a>Adjust TCP system parameters to reduce TCP/IP timeouts</li></ul></li></ul> <a name= "1015038"></a> <p class="BP">Follow this recommendation for all databases:</p> <ul class="LB1"> <li class="LB1" type="disc"><a name= "1015039"></a><a href="configbp.htm#1015185">Configure Services</a></li></ul> <a name="1015041"></a> <p class="BP">Follow these reco mmendation for RAC:</p> <ul class="LB1"> <li class="LB1" type="disc"><a name="1015042"></a><a href="configbp.htm#1015188">Configure C RS for High Availability</a></li> <li class="LB1" type="disc"><a name="1015043"></a><a href="configbp.htm#1015201">Configure Service Callouts to Notify Middle-Tier Applications and Clients</a></li></ul> <a name="1015045"></a> <p class="BP">Follow these recommendati ons for Data Guard, replicated, or distributed environments:</p> <ul class="LB1"> <li class="LB1" type="disc"><a name="1015046"></a>< a href="configbp.htm#1015215">Publish Standby or Nonproduction Services</a></li> <li class="LB1" type="disc"><a name="1015047"></a><a href="configbp.htm#1015220">Publish Production Services</a></li></ul> <a name="1015051"></a>  <h3 class="H2"> <font face="Arial, Helvetica, sans-serif" color="#330099">Configure Connection Descriptors for All Possible Production Instances</fon t></h3>  <a name="1015052"></a> <p class="BP">Clients and mid-tier applications make connection requests by specifying a service using a global name. The connection information must be aware of all potential production instances or databases that are capable of publishing that service. Furthermore, these connection descriptors should ideally be stored in an LDAP or Oracle Name serv er for ease of maintenance and administration.</p> <a name="1017349"></a> <p class="BP">This section includes three sample Oracle Ne t connection descriptors. Use the <code>PROD_RAC</code> connection descriptor in <a href="configbp.htm#1015058">Example 7-1</a>w hen there is no standby database available or if DNS site failover is deployed.</p> <a name="1017355"></a> <p class="BP">The <code>P ROD_RAC_DG</code> connection descriptor in <a href="configbp.htm#1015070">Example 7-2</a> has an address list that contains all production RAC instances and the Data Guard standby instances. This example can be used in the case of a production database outage w hen the hardware cluster is still available. It helps you avoid TCP/IP timeouts.</p> <a name="1017365"></a> <p class="BP">When the e ntire hardware cluster fails, the connection needs to be manually adjusted to point to the standby database using the connection desc riptor provided in <a href="configbp.htm#1015084">Example 7-3</a>.</p> <a name="1017372"></a> <p class="BP">For disaster recove ry, client-side DNS failover or site failover is recommended over listing both production instances and standby database instances.</ p> <a name="1017469"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="l tr" summary="This is a layout table to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td clas s="NoteAlso"><a name="1017472"></a><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="10 17473"></a> <p class="NB"><a href="recover.htm#1006233">"Complete or Partial Site Failover"</a><a href="recover.htm#1006233"></a></p ></td></tr></table></div> <a name="1015058"></a> <h4 class="ET"><font face="Arial, Helvetica, sans-serif"><em>Example 7-1 Connection Descriptor: No Standby Database Available or DNS Site Failover is Deployed</em></font></h4> <pre class="CE"><a name="1015060"></a>PR OD_RAC= <a name="1015061"></a> (DESCRIPTION = <a name="1015062"></a> (ADDRESS_LIST = <a name="1015063"></a> (LOAD_BALANCE=on ) <a name="1015064"></a> (ADDRESS = (PROTOCOL = TCP)(HOST = RAC_INSTANCE1)(PORT = 1520)) <a name="1015065"></a> (ADDRESS = (PROTOCOL = TCP)(HOST = RAC_INSTANCE2)(PORT = 1520)) <a name="1015066"></a> (ADDRESS = (PROTOCOL = TCP)(HOST = RAC_INSTANCE3)( PORT = 1520)) <a name="1015067"></a> (ADDRESS = (PROTOCOL = TCP)(HOST = RAC_INSTANCE4)(PORT = 1520)) <a name="1015068"></a> ( CONNECT_DATA = <a name="1015069"></a> (SERVICE_NAME = MAA_PROD))) </pre> <a name="1015070"></a> <h4 class="ET"><font face="Aria l, Helvetica, sans-serif"><em>Example 7-2 Connection Descriptor: Production Database Outage When Hardware Cluster is Available</em></ font></h4> <pre class="CE"><a name="1015072"></a>PROD_RAC_DG= <a name="1015073"></a> (DESCRIPTION = <a name="1015074"></a> (ADDRE SS_LIST = <a name="1015075"></a> (LOAD_BALANCE=on) <a name="1015076"></a> (ADDRESS = (PROTOCOL = TCP)(HOST = RAC_INSTANCE 1)(PORT = 1520)) <a name="1015077"></a> (ADDRESS = (PROTOCOL = TCP)(HOST = RAC_INSTANCE2)(PORT = 1520)) <a name="1015078"></a> (ADDRESS = (PROTOCOL = TCP)(HOST = RAC_INSTANCE3)(PORT = 1520)) <a name="1015079"></a> (ADDRESS = (PROTOCOL = TCP)(HOST = RA C_INSTANCE4)(PORT = 1520)) <a name="1015080"></a> (ADDRESS = (PROTOCOL = TCP)(HOST = DG_INSTANCE1)(PORT = 1520)) <a name="101508 1"></a> (ADDRESS = (PROTOCOL = TCP)(HOST = DG_INSTANCE2)(PORT = 1520))) <a name="1015082"></a> (CONNECT_DATA = <a name="10150 83"></a> (SERVICE_NAME = MAA_PROD))) </pre> <a name="1015084"></a> <h4 class="ET"><font face="Arial, Helvetica, sans-serif"><em >Example 7-3 Connection Descriptor: Hardware Cluster Fails</em></font></h4> <pre class="CE"><a name="1015086"></a>PROD_DR= <a name="1 015087"></a> (DESCRIPTION = <a name="1015088"></a> (ADDRESS_LIST = <a name="1015089"></a> (LOAD_BALANCE=on) <a name="10150 90"></a> (ADDRESS = (PROTOCOL = TCP)(HOST = DG_INSTANCE1)(PORT = 1520)) <a name="1015091"></a> (ADDRESS = (PROTOCOL = TCP)(HOST = DG_INSTANCE2)(PORT = 1520))) <a name="1015092"></a> (CONNECT_DATA = <a name="1015093"></a> (SERVICE_NAME = MAA_PR OD))) </pre> <a name="1015094"></a> <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099"> Use RAC Availability Notifications and Events</font></h3>  <a name="1016994"></a> <p class="BP">Ideally, the middle-ti er applications and clients should use the automatic RAC availability notifications and events. Applications that use Oracle Database 10<em class="Italic">g</em> JDBC fast connection failover subscribe to these events automatically. Other applications may need to co nfigure these service callouts and modify the applications to react to them.</p> <a name="1016995"></a> <div align="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" t itle="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1016998"></a><font face="Arial, H elvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1016999"></a> <ul class="NL"> <li class="NL" type="disc" ><a name="1017025"></a><a href="configbp.htm#1015201">"Configure Service Callouts to Notify Middle-Tier Applications and Clients"</a> <a href="configbp.htm#1015201"></a></li> <li class="NL" type="disc"><a name="1017012"></a><em class="Italic"><a class="olinkSRC JJDBC " href="../../java$101/b10979/toc.htm">Oracle Database JDBC Developer's Guide and Reference</a></em></li></ul></td></tr></table></div > <a name="1015730"></a>  <h3 class="H2"><a name="MAXAV081"><font face="Arial, Helvetica, sans-serif" color="# 330099">Use Transparent Application Failover If RAC Notification Is Not Feasible</font></a></h3>  <a name="1015731"></a > <p class="BP">If you cannot use RAC notification or if RAC is not deployed, then use Transparent Application Failover (TAF). When Oracle Call Interface (OCI) client applications are used, Transparent Application Failover (TAF) can be configured to transparently f ail over connections between an application server and a database server.</p> <a name="1015106"></a> <p class="BP">OCI client applic ations can take advantage of automatic reconnection after failover and callback functions that help to automate state recovery. They can also replay interrupted <code>SELECT</code> statements and callback functions that help to automate state recovery. The Oracle JD BC and ODBC drivers also support automatic database reconnection and replay of interrupted <code>SELECT</code> statements without the need for any additional application coding.</p> <a name="1015107"></a> <p class="BP">The TAF configuration is specified in the conn ect string that clients use to connect to the database.</p> <a name="1015109"></a> <p class="BP">The following sample TAF connection descriptor is used to describe the impact of TAF and how to use each component.</p> <pre class="CE"><a name="1015114"></a>PROD= <a n ame="1015115"></a> (DESCRIPTION = <a name="1015116"></a> (FAILOVER=on) <a name="1015117"></a> (ADDRESS_LIST = <a name="1015118 "></a> (LOAD_BALANCE=on) <a name="1015119"></a> (ADDRESS = (PROTOCOL = TCP)(HOST = RAC_INSTANCE1)(PORT = 1520)) <a name=" 1015120"></a> (ADDRESS = (PROTOCOL = TCP)(HOST = RAC_INSTANCE2)(PORT = 1520)) <a name="1015121"></a> (ADDRESS = (PROTOCOL = TCP)(HOST = RAC_INSTANCE3)(PORT = 1520)) <a name="1015122"></a> (ADDRESS = (PROTOCOL = TCP)(HOST = RAC_INSTANCE4)(PORT = 1520)) <a name="1015123"></a> (ADDRESS = (PROTOCOL = TCP)(HOST = DG_INSTANCE1)(PORT = 1520)) <a name="1015124"></a> (ADDRESS = (P ROTOCOL = TCP)(HOST = DG_INSTANCE2)(PORT = 1520))) <a name="1015125"></a> (CONNECT_DATA = <a name="1015126"></a> (SERVICE_NAM E = MAA_PROD) <a name="1015127"></a> (FAILOVER_MODE = <a name="1015128"></a>(BACKUP=PROD_BACKUP)(TYPE=SESSION)(METHOD=BASIC) <a n ame="1015129"></a>(RETRIES=12)(DELAY=5)))) <a name="1015130"></a> <a name="1015131"></a>PROD_BACKUP= <a name="1015132"></a> (DESCRIP TION = <a name="1015133"></a> (FAILOVER=on) <a name="1015134"></a> (ADDRESS_LIST = <a name="1015135"></a> (LOAD_BALANC E=on) <a name="1015136"></a> (ADDRESS = (PROTOCOL = TCP)(HOST = RAC_INSTANCE1)(PORT = 1520)) <a name="1015137"></a> (ADD RESS = (PROTOCOL = TCP)(HOST = RAC_INSTANCE2)(PORT = 1520)) <a name="1015138"></a> (ADDRESS = (PROTOCOL = TCP)(HOST = RAC_INSTAN CE3)(PORT = 1520)) <a name="1015139"></a> (ADDRESS = (PROTOCOL = TCP)(HOST = RAC_INSTANCE4)(PORT = 1520)) <a name="1015140"></a> (ADDRESS = (PROTOCOL = TCP)(HOST = DG_INSTANCE1)(PORT = 1520)) <a name="1015141"></a> (ADDRESS = (PROTOCOL = TCP)(HOST = D G_INSTANCE2)(PORT = 1520))) <a name="1015142"></a> (CONNECT_DATA = <a name="1015143"></a> (SERVICE_NAME = MAA_PROD) <a name=" 1015144"></a> (FAILOVER_MODE = <a name="1015145"></a>(BACKUP=PROD)(TYPE=SESSION)(METHOD=BASIC) <a name="1015146"></a>(RETRIES=1 2)(DELAY=5)))) </pre> <a name="1015254"></a> <h4 class="H3"><font face="Arial, Helvetica, sans-serif" color=" #330099">New Connections</font></h4>  <a name="1015154"></a> <p class="BP">New connections use the address list and co nnect to the first available listener that has the service (<code>MAA_PROD</code>) registered. This is true for both instance and lis tener failure. If there is an attempt to connect to a failed node, then a TCP/IP timeout occurs. Retries and delay have no effect on new connections because new connections attempt the address list only once.</p> <a name="1015360"></a>  <h4 cl ass="H3"><font face="Arial, Helvetica, sans-serif" color="#330099">Existing Connections</font></h4>  <a name="1015156"> </a> <p class="BP">Existing connections use the backup connection descriptor and wait the number of seconds specified by <code>DELAY </code> between each iteration. After attempting all addresses in the backup connection descriptor, the client waits the number of se conds specified by <code>DELAY</code> before attempting the address list again. The client retries the address list up to the number of times specified by <code>RETRIES</code>. If the service is not available anywhere after the number of seconds that is equal to <co de>RETRIES</code> times <code>DELAY</code>, then the client receives an ORA-3113 error. The maximum switchover or failover times shou ld be less than <code>RETRIES*DELAY</code> if you want automatic client failover to a disaster recovery site.</p> <a name="1015158">< /a>  <h4 class="H3"><font face="Arial, Helvetica, sans-serif" color="#330099">LOAD_BALANCE Parameter in the Co nnection Descriptor</font></h4>  <a name="1015361"></a> <p class="BP"><code>LOAD_BALANCE</code> sets the client-side l oad balancing. When it is set to <code>ON</code>, the client randomly selects an address from the address list. If a listener has mul tiple instances registered with it that offer the same service, then the listener can balance client requests between the instances b ased on the load on the instances at that time.</p> <a name="1015159"></a>  <h4 class="H3"><font face="Arial, Helvetica, sans-serif" color="#330099">FAILOVER Parameter in the Connection Descriptor</font></h4>  <a name="1015160">< /a> <p class="BP">Set <code>FAILOVER</code> to <code>ON</code>. The client fails through the address list if one or more of the serv ices, instances, listeners, or nodes on the list is down or not available.</p> <a name="1015161"></a>  <h4 cla ss="H3"><font face="Arial, Helvetica, sans-serif" color="#330099">SERVICE_NAME Parameter in the Connection Descriptor</font></h4> <!- -/TOC=h3--> <a name="1015162"></a> <p class="BP">The service name is published by the database to the listener.</p> <a name="1015163 "></a>  <h4 class="H3"><font face="Arial, Helvetica, sans-serif" color="#330099">RETRIES Parameter in the Conn ection Descriptor</font></h4>  <a name="1015164"></a> <p class="BP">This parameter determines how many times an existi ng connection retries the addresses in the <code>BACKUP</code> list or after a failover. This parameter has no effect on new connecti ons. New clients go through the address list only once.</p> <a name="1015165"></a>  <h4 class="H3"><font face= "Arial, Helvetica, sans-serif" color="#330099">DELAY Parameter in the Connection Descriptor</font></h4>  <a name="10151 66"></a> <p class="BP">This parameter determines the number of seconds the client waits between each retry. After going through the address list, the client waits for the number of seconds specified by <code>DELAY</code> before retrying. There is no delay between i ndividual addresses in the address list. The delay applies only after the whole list has been traversed.</p> <a name="1015426"></a> <p class="BP">With RAC, TCP/IP timeouts due to an unavailable node in a cluster are avoided because RAC manages a Virtual Internet Pr otocol (VIP) and cluster alias. However, TCP/IP timeouts cannot be avoided when the entire cluster or non-RAC host is not available. To avoid this TCP/IP timeout, the customer should do one of the following:</p> <ul class="LB1"> <li class="LB1" type="disc"><a name=" 1015427"></a>Create a special event and callout to detect and react to such as event</li> <li class="LB1" type="disc"><a name="101542 8"></a>Adjust TCP/IP parameters to reduce overall timeout impact</li></ul> <a name="1015178"></a> <p class="BP">The customized callo ut should interrupt existing connections and redirect new connections with a new connection descriptor that does not contain the unav ailable nodes or clusters.</p> <a name="1015180"></a> <p class="BP">Adjusting TCP/IP parameters may have other application and syste m impact, so always use caution. However, the following TCP/IP parameters were modified on a Solaris platform to reduce overall TCP/I P timeout intervals in Oracle testing:</p> <ul class="LB1"> <li class="LB1" type="disc"><a name="1015181"></a><code>tcp_ip_abort_cint erval</code></li> <li class="LB1" type="disc"><a name="1015182"></a><code>tcp_ip_abort_interval</code></li> <li class="LB1" type="dis c"><a name="1015183"></a><code>tcp_keepalive_interval</code></li></ul> <a name="1017052"></a> <p class="BP">Check your operating sys tem platform documentation for similar parameters.</p> <a name="1015185"></a>  <h3 class="H2"><font face="Aria l, Helvetica, sans-serif" color="#330099">Configure Services</font></h3>  <a name="1015186"></a> <p class="BP">Within RAC, use the Database Configuration Assistant (DBCA), Server Control (<code>SRVCTL</code>), or the <code>DBMS_SERVICE</code> PL/SQL p ackage to create services. Then use the DBCA or Enterprise Manager to administer them. If this is a non-RAC environment, then set the <code>SERVICE_NAME</code> database initialization parameter.</p> <a name="1015188"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Configure CRS for High Availability</font></h3>  <a name="1015189" ></a> <p class="BP">CRS supports services and the workload management framework that maintains continuous availability of the servic es. CRS also supports the other RAC resources such as the database, the database cluster aliases, and the resources that are local to every node that supports RAC.</p> <a name="1015190"></a> <p class="BP">Node resources include the virtual internet protocol (VIP) a ddress for the node, the Global Services Daemon, the Enterprise Manager Agent, and the Oracle Net listeners. These resources are auto matically started when CRS starts with the node and CRS automatically restarts them if they fail.</p> <a name="1015467"></a> <div al ign="center"> <table class="NoteAlso" border="0" width="80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout tabl e to format a note" title="This is a layout table to format a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1015470"></a ><font face="Arial, Helvetica, sans-serif"><strong class="NH">See Also:</strong></font> <a name="1015471"></a> <ul class="NL"> <li c lass="NL" type="disc"><a name="1015472"></a><em class="Italic"><a class="olinkSRC RACAD" href="../../rac$101/b10765/toc.htm">Oracle R eal Application Clusters Administrator's Guide</a></em></li> <li class="NL" type="disc"><a name="1015479"></a><em class="Italic"><a c lass="olinkSRC RACDP" href="../../rac$101/b10768/toc.htm">Oracle Real Application Clusters Deployment and Performance Guide</a></em>< /li></ul></td></tr></table></div> <a name="1015201"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-se rif" color="#330099">Configure Service Callouts to Notify Middle-Tier Applications and Clients</font></h3>  <a name="10 15202"></a> <p class="BP">Configure service callouts to notify middle-tier applications and clients about <code>UP</code>, <code>DOW N</code>, and <code>NOT_RESTARTING</code> events. RAC automatically notifies JDBC clients through JDBC fast connection failover witho ut any adjustments. In the rare case that the entire RAC cluster fails, a separate notification and callout is required to notify the middle-tier applications to connect to a disaster recovery or secondary database.</p> <a name="1015204"></a> <p class="BP">If the m iddle-tier application or clients are not JDBC clients, then you must use RAC's event management and service callout facilities to co nfigure a customized callout. The callout needs to notify the middle-tier application to do the following:</p> <ul class="LB1"> <li c lass="LB1" type="disc"><a name="1015205"></a>Interrupt existing connections to problematic or unavailable nodes or instances</li> <li class="LB1" type="disc"><a name="1015206"></a>Redirect new connections to available production instances or nodes</li></ul> <a name= "1015208"></a> <p class="BP">Interrupting existing connections helps avoid long TCP/IP timeout delays. Redirecting new connections t o available production instances or nodes may require passing a new connection descriptor that does not include any inaccessible host s so that TCP/IP timeouts can be avoided.</p> <a name="1015511"></a> <div align="center"> <table class="NoteAlso" border="0" width=" 80%" cellpadding="0" cellspacing="0" dir="ltr" summary="This is a layout table to format a note" title="This is a layout table to for mat a note"> <tr class="NoteAlso"> <td class="NoteAlso"><a name="1015514"></a><font face="Arial, Helvetica, sans-serif"><strong class ="NH">See Also:</strong></font> <a name="1015515"></a> <p class="NB"><em class="Italic"><a class="olinkSRC RACAD" href="../../rac.10 1/b10765/toc.htm">Oracle Real Application Clusters Administrator's Guide</a></em></p></td></tr></table></div> <a name="1015215"></a>  <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Publish Standby or Nonproduction Ser vices</font></h3>  <a name="1015216"></a> <p class="BP">When RAC and Enterprise Manager are integrated, standby or non production services can be published automatically. If the standby database is not managed by Enterprise Manager or is not part of a RAC environment, then you can manually alter the <code>SERVICE_NAME</code> database initialization parameter to be a nonproduction se rvice. For example:</p> <pre class="CE"><a name="1015218"></a>SQL> ALTER SYSTEM SET SERVICE_NAME='STANDBY'; </pre> <a name="10152 20"></a> <h3 class="H2"><font face="Arial, Helvetica, sans-serif" color="#330099">Publish Production Services< /font></h3>  <a name="1015221"></a> <p class="BP">When RAC and Enterprise Manager are integrated, production services can be published automatically. If the new production database is not managed by Enterprise Manager or is not part of a RAC environme nt, then you can manually alter the <code>SERVICE_NAME</code> database initialization parameter to be set to different production ser vices. For example:</p> <pre class="CE"><a name="1015223"></a>SQL> ALTER SYSTEM SET SERVICE_NAME='<em class="Italic">PROD_SVC1</em >, <em class="Italic">PROD_SVC2</em>, <em class="Italic">PROD_SVC3</em>'; <a name="1015540"></a> </pre> <a name="1015224"></a> <p c lass="BP"><em><code>PROD_SVC1</code></em> can be <code>SALES</code> or <code>HR</code>, for example.</p></div> <div class="footer"> < hr> <table summary="" cellspacing="0" cellpadding="0" width="100%"> <tr> <td style="width: 33%;" align="left"> <table summary="layout table" cellspacing="0" cellpadding="0" align="left" width="90"> <tr> <td align="center" valign="top"><a href="sysnet.htm"><img src=" ../../dcommon/gifs/larrow.gif" alt="Go to previous page" border="0"><br> <font size="-2">Previous</font></a></td> <td align="center" valign="top"><a href="partpage4.htm"><img src="../../dcommon/gifs/rarrow.gif" alt="Go to next page" border="0"><br> <font size="-2">N ext</font></a></td></tr></table></td> <td style="width: 34%;" align="center"><img src="../../dcommon/gifs/oracle.gif" alt="Oracle"><b r> <a href="../../dcommon/html/cpyr.htm"><font size="-2">Copyright © 2003 Oracle Corporation</font></a><br> <font size="-2">All Rights Reserved.</font></td> <td style="width: 33%;" align="right"> <table summary="" cellspacing="0" cellpadding="0" width="270"> <t r> <td align="center" valign="top"><a href="../../index.htm"><img src="../../dcommon/gifs/prodicon.gif" alt="Go to Documentation Home " border="0"><br> <font size="-2">Home</font></a></td> <td align="center" valign="top"><a href="../../nav/portal_3.htm"><img src="../ ../dcommon/gifs/bookicon.gif" alt="Go to Book List" border="0"><br> <font size="-2">Book List</font></a></td> <td align="center" vali gn="top"><a href="toc.htm"><img src="../../dcommon/gifs/conticon.gif" alt="Go to Table of Contents" border="0"><br> <font size="-2">C ontents</font></a></td> <td align="center" valign="top"><a href="index.htm"><img src="../../dcommon/gifs/indxicon.gif" alt="Go to Ind ex" border="0"><br> <font size="-2">Index</font></a></td> <td align="center" valign="top"><a href="../../mix$101/b12039/toc.htm"><img src="../../dcommon/gifs/mix.gif" alt="Go to Master Index" border="0"><br> <font size="-2">Master Index</font></a></td> <td alig n="center" valign="top"><a href="../../dcommon/html/feedback.htm"><img src="../../dcommon/gifs/feedback.gif" alt="Go to Feedback page " border="0"><br> <font size="-2">Feedback</font></a></td></tr></table></td></tr></table></div> </body> </html>