16 DBVERIFY: Offline Database Verification Utility

DBVERIFY is an external command-line utility that performs a physical data structure integrity check. It can be used on offlin e or online databases, as well on backup files. You use DBVERIFY primarily when you need to ensure that a backup database (or datafil e) is valid before it is restored, or as a diagnostic aid when you have encountered data corruption problems.

Because DBVERIFY can be run against an offline database, integrity checks are significantly faster.

D BVERIFY checks are limited to cache-managed blocks (that is, data blocks). Because DBVERIFY is only for use with datafiles, it will n ot work against control files or redo logs.

There are two command-line interfaces to DBVERIFY. With the first interface, you s pecify disk blocks of a single datafile for checking. With the second interface, you specify a segment for checking. Both interfaces are started with the dbv command. The following sections provide descriptions of these interfaces:

Using DBVERIFY to Validate Disk Blocks of a Single Datafile
Using DBVERIFY to Validate a Segment

Using DBVERIFY to Validate Disk Blocks o f a Single Datafile

In this mode, DBVERIFY scans one or more disk blocks of a single datafile and performs page checks.

No te:

If the file you are verifying is an Automatic Storage Management (ASM) file, you must supply a USERID. This is because DBVERIFY needs to connect to an Oracle instance to access ASM files.

Syntax

The synt ax for DBVERIFY when you want to validate disk blocks of a single datafile is as follows:

Description of the illustration dbverify.gif

Parameters

Descriptions of the parameters are as f ollows:

USERID

Parameter	Description
Specifies your user name and password. This parameter is only necessary when the files being verified are ASM files.
`FILE`	The name of th e database file to verify.
`START`	The starting block address to verify. Specify block addresses in Oracle blocks (as opposed to operating system blocks). If you do not specify `START`, DBVERIFY defaults to the first block in the file.
`END`	The ending block address to verify. If you do not specify `END`, DBVERIFY defaults to the last block in t he file.
`BLOCKSIZE`	`BLOCKSIZE` is required only if the file to be verified does not have a block size of 2 KB. If the file does not have block size of 2 KB and you do not specify `BLOCKSIZE`, you will receive the error DBV-0010 3.
`LOGFILE`	Specifies the file to which logging information should be written. The default sends output to the termin al display.
`FEEDBACK`	Causes DBVERIFY to send a progress display to the terminal in the form of a single period (.) f or `n` number of pages verified during the DBVERIFY run. If `n` = 0, there is no progress dis play.
`HELP`	Provides online help.
`PARFILE`	Specifies the name of the parameter file to use. You can store various values for DBVERIFY parameters in flat files. This enables you to customize parameter files to handle different types of datafiles and to perform specific types of integrity checks on datafiles.

Command-Line Interface

The following example shows a sample use of the command-line interface to this mode of DBVERIFY.

% dbv FILE=t_db1.dbf FEEDBACK=100

Sample DBVERIFY Output

The following is a sample verification of the file t_db1.dbf.The feedback parameter has been given the value 100 to display one period (.) for every 100 pages processed. A portion of the resulting output is also shown.

% dbv FILE=t_db1.dbf FE
EDBACK=100
.
.
.
DBVERIFY - Verification starting : FILE = t_db1.dbf 

..............................................................
..................
 

DBVERIFY - Verification complete 
 
Total Pages Examined         : 9216 
Total Pages Processed (Data) : 2044 
T
otal Pages Failing   (Data) : 0 
Total Pages Processed (Index): 733 
Total Pages Failing   (Index): 0 
Total Pages Empty            :
 5686 
Total Pages Marked Corrupt   : 0 

Total Pages Influx           : 0

Notes:

Pages = Blocks
Total Pages Examined = number of blocks in the file
T otal Pages Processed = number of blocks that were verified (formatted blocks)
Total Pages Failing (Data) = number of blocks that failed the data block checking routine
Total Pages Failing (Index) = number of blocks that failed the index block checking routine
Total Pages Marked Corrupt = number of blocks for wh ich the cache header is invalid, thereby making it impossible for DBVERIFY to identify the block type
To tal Pages Influx = number of blocks that are being read and written to at the same time. If the database is open when DBVERIFY is run , DBVERIFY reads blocks multiple times to get a consistent image. But because the database is open, there may be blocks that are bein g read and written to at the same time (INFLUX). DBVERIFY cannot get a consistent image of pages that are in flux.

Using DBVERIFY to Validate a Segment

In this mode, DBVERIFY enables you to specify a table segment or index segment for verif ication. It checks to make sure that a row chain pointer is within the segment being verified.

This mode requires that you spe cify a segment (data or index) to be validated. It also requires that you log on to the database with SYSDBA privileges, because information about the segment must be retrieved from the database.

During this mode, the segment is locked. If the sp ecified segment is an index, the parent table is locked. Note that some indexes, such as IOTs, do not have parent tables.

Syntax
The syntax for `DBVERIFY` when you want to validate a segment is as follows:

Description of the illustration dbverify_seg.gif

Parameters

Descriptions of the parameters a re as follows:

Parameter	Description
`USERID`	Specifies your username and password.
`SEGMENT_ID`	Specifies the segment that you want to verify. You can identify the `tsn`, `segfile`, and `seg block` by joining and querying the appropriate data dictionary tables, for example, `USER_TABLES` and `USER_SEG MENTS.`
`LOGFILE`	Specifies the file to which logging information should be written. The default sends output to the terminal display.
`FEEDBACK`	Causes DBVERIFY to send a progress display to the terminal in the form of a single p eriod (.) for `n` number of pages verified during the DBVERIFY run. If `n` = 0, there is no p rogress display.
`HELP`	Provides online help.
`PARFILE`	Specifies the name of the parameter file to use . You can store various values for DBVERIFY parameters in flat files. This enables you to customize parameter files to handle differe nt types of datafiles and to perform specific types of integrity checks on datafiles.

Command-Line Interface

The following example shows a sample use of the com mand-line interface to this mode of DBVERIFY.

dbv USERID=username/password SEGMENT_ID
=tsn.segfile.segblock

16 DBVERIFY: Offline Database Verification Utility

Using DBVERIFY to Validate Disk Blocks o f a Single Datafile

Syntax

Parameters

Command-Line Interface

Sample DBVERIFY Output

Using DBVERIFY to Validate a Segment

Syntax The syntax for DBVERIFY when you want to validate a segment is as follows: Description of the illustration dbverify_seg.gif

Parameters

Command-Line Interface

Syntax
The syntax for `DBVERIFY` when you want to validate a segment is as follows:

Description of the illustration dbverify_seg.gif