Understanding DB2: Learning Visually with Examples (2nd Edition)

13.3. Recovery Terminology

Depending on the type of backups that you take, there are different methods that you can use to recover your database in the event of an error. In addition, the configuration you choose for your database will determine whether you can use the database logs to reapply transactions that might otherwise be lost if you need to restore your database from a backup.

13.3.1. Logging Methods Versus Recovery Methods

Circular logging supports only crash and version recovery. Archival logging supports all types of recovery: crash, version, and roll forward.

13.3.2. Recoverable Versus Nonrecoverable Databases

Recoverable databases can be recovered using crash or roll forward recovery, and as discussed before, archival logging is required to support roll forward recovery . Nonrecoverable databases do not support roll forward recovery and use only circular logging. Table 13.2 shows which logging and recovery methods work together.

Table 13.2. Summary of Logging and Recovery Methods

Logging Method

Supports Crash Recovery

Supports Version Recovery

Supports Roll Forward Recovery

Recoverable Database

Circular Logging (LOGARCHMETH1 = OFF)

Yes

Yes

No

No

Archival Logging (LOGARCHMETH1 = LOGRETAIN, USEREXIT, DISK, TSM, or VENDOR)

Yes

Yes

Yes

Yes

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