Oracle ASM disk scrubbing improves availability and reliability by searching for data that may be less likely to be read. Disk scrubbing checks logical data corruptions and repairs them automatically in normal and high redundancy disks groups. The scrubbing process repairs logical corruptions using the mirror disks. Disk scrubbing can be combined with disk group rebalancing to reduce I/O resources. The disk scrubbing process has minimal impact to the regular I/O in production systems.
You can perform scrubbing on a disk group, a specified disk, or a specified file of a disk group with the ALTER DISKGROUP SQL statement. For example, the following SQL statements show various options used when running the ALTER DISKGROUP disk_group SCRUB SQL statement.
SQL> ALTER DISKGROUP data SCRUB POWER LOW;
SQL> ALTER DISKGROUP data SCRUB FILE '+DATA/ORCL/DATAFILE/example.266.806582193'
REPAIR POWER HIGH FORCE;
SQL> ALTER DISKGROUP data SCRUB DISK DATA_0005 REPAIR POWER HIGH FORCE;
When using ALTER DISKGROUP with the SCRUB option, the following items apply:
The optional REPAIR option automatically repairs disk corruptions. If the REPAIR option is not specified, then the SCRUB option only checks and reports logical corruptions of the specified target.
The optional POWER value can be set to AUTO, LOW, HIGH, or MAX. If the POWER option is not specified, the power value defaults to AUTO and the power adjusts to the optimum level for the system.
If the optional WAIT option is specified, the command returns after the scrubbing operation has completed. If the WAIT option is not specified, the scrubbing operation is added into the scrubbing queue and the command returns immediately.
If the optional FORCE option is specified, the command is processed even if the system I/O load is high or scrubbing has been disabled internally at the system level.
The scrubbing process is visible in the fields of the V$ASM_OPERATION view while the scrubbing process is running.