Databases Reference
In-Depth Information
Another useful feature of the
validate
command is that you can instruct it to validate all files required for
recovery: backup pieces, archive redo log files, data file copies, and control file auto backups. For example:
RMAN> validate recovery files;
The prior command validates files whether they exist in the FRA or not. It does not validate that flashback logs
exist and are available.
To validate all backup pieces in the FRA, use either of the following commands:
RMAN> validate recovery area;
RMAN> validate db_recovery_file_dest;
How It Works
When you validate backup sets, RMAN actually reads the backup files as if it were doing a restore operation, except
that no files are restored or written to disk. This will indicate how much time it takes to read the files during a real
restore operation (this could be useful for troubleshooting I/O problems).
The validate clause works with any
restore
command; here are some examples:
RMAN> restore database from tag MON_BCK validate;
RMAN> restore datafile 1 validate;
RMAN> restore archivelog all validate;
RMAN> restore controlfile validate;
RMAN> restore tablespace users validate;
■
Tip
periodically run the
restore ... validate
as part of testing the viability of your backups.
If you have large backup sets, the
restore ... validate
command can take some time to complete. You can
use the
header
clause to instruct RMAN to check only if the required backup files exist on disk (and not validate its
structure). For example:
RMAN> restore database validate header;
By default the
restore ... validate
command and the
validate
command check only for physical corruption.
Use the
check logical
parameter if you want the validation process to also check for logical corruption:
RMAN> validate backupset 42 check logical;
When RMAN detects logical corruption, it will write relevant error messages to your target database's alert.log file
and also reflect this information in the V$DATABASE_BLOCK_CORRUPTION view.
You can see whether a corrupt block is either physically or logically corrupt by querying the CORRUPTION_TYPE
column of the V$DATABASE_BLOCK_CORRUPTION view. RMAN can perform block media recovery only on
physically corrupt blocks. Blocks tagged with type LOGICAL corruption cannot be recovered by RMAN (through
block-level recovery). To recover logically corrupt blocks, restore the data file from a backup and perform
media recovery.
