ASM provides automatic recovery for disk failures. When a disk fails, ASM reconfigures all ASM-managed files in the disk group with the failed disk and removes the failed disk from the disk group. This is known as a rebalance.
When Replication Agent for Oracle detects a disk failure, it automatically switches to reading disk group mirrors. If the disk group is configured to have the mirror and mirror copy, Replication Agent for Oracle can recover from multiple disk failures. If the disk group is configured for no mirroring or if too many disks have failed and the log cannot be read, Replication Agent for Oracle checks to see if an ASM rebalance is occurring or has occurred. Log device information is updated with new ASM information when the rebalance is complete. The time required for a complete rebalance can vary, depending on how many disk are in the failing disk group.
Log device information can be manually updated by issuing the ra_updatedevices command. If a disk group must be changed by adding or removing a disk, ra_updatedevices can be issued to ensure log devices obtain the new disk group configuration. This command must be issued only after the disk group is changed and ASM has completed its rebalance.
If Replication Agent for Oracle cannot recover on its own from a disk failure or disk group change, ra_updatedevices can be used to update log device information before resuming replication.
