Data recovery after disk failures for distributed relational databases

Recovery is not possible for recently entered data if a disk failure occurs and all objects are not saved on tape or disk immediately before the failure. After previously saved objects are restored, the server is operational, but the database is not current.

Auxiliary storage pools (ASPs), checksum protection, and mirrored protection are i5/OS™ disk recovery functions that provide methods to recover recently entered data after a disk-related failure. These functions use additional server resources, but provide a high level of protection for servers in a distributed relational database. Because some servers might be more critical as application servers than others, the distributed relational database administrator should review how these disk data protection methods can be best used by individual servers within the network.

• Auxiliary storage pools
  An auxiliary storage pool (ASP) is one or more physical disk units assigned to the same storage area. ASPs allow you to isolate certain types of objects on specified physical disk units.
• Checksum protection in a distributed relational database
  Checksum protection guards against data loss on any disk in an auxiliary storage pool (ASP).
• Mirrored protection for a distributed relational database
  Mirrored protection increases the availability of a server by duplicating different disk-related hardware components, such as a disk controller, a disk I/O processor, or a bus. The server can remain available after a failure, and service for the failed hardware components can be scheduled at a convenient time.