Monday, January 29, 2018

Testing ASM Disk Failure Scenario and disk_repair_time

When a disk failure occurs for an ASM disk, behavior of ASM would be different, based on what kind of redundancy for the diskgroup is in use. If diskgroup has EXTERNAL REDUDANCY, diskgroup would keep working if you have redundancy at external RAID level. If there is no RAID at external level, the diskgroup would immediately get dismounted and disk would need a repair/replaced and then diskgroup might need to be dropped and re-created, and data on this diskgroup would require recovery.

Monday, January 22, 2018

ORA-00845: MEMORY_TARGET not supported on this system

If we face ORA-00845 during database startup, it would mean that /dev/shm file system is not configured with appropriate value required to start the database instance. We need to mount /dev/shm with a value that should be equal or more than the value of memory we want to allocate to all instances/SGAs (ASM as well as database instances) that would run on this host.
You may find following type of warning in alert log file.

Monday, January 8, 2018


I faced an issue recently where my CROSSCHECK and DELETE OBSOLETE commands were too much slow to execute, actually these were hung. The reason for this issue was IP address change of my NFS server form where a drive was mounted on database server for backups and backups were being taken on this NFS share. After NFS server’s IP address change, RMAN would go to check old IP address to search for the old/obsolete backups when we executed CROSSCHECK and DELETE OBSOLETE commands.

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