RFUTIL AIMAGE TRUNCATE qualifier

Truncates all of the variable-length AIextents and optionally sets the AI block size with the After-image Block Size (-aiblocksize) parameter.

Syntax

rfutil db-name -C aimage truncate -aiblocksize size

Parameters

db-name

Specifies the database you are using.

-aiblocksize size

Specifies the size of the AI blocks in each buffer, in kilobytes. The valid values are 1, 2, 4, 8, and 16. The block size cannot be smaller than the database block size.

Notes

After running this command to change the AI block size, you must perform a full backup of the database before you can re-enable after-imaging. If you change the BI block size or cluster size before backing up the database, the block size of the backup will overwrite the changed block size when the backup is restored.

Increasing the AI block size allows larger AI reads and writes. This can reduce I/O rates on disks where the AI areas are located. If your operating system can benefit from larger writes, this option can improve performance. Larger AI block size might also improve performance for roll-forward recovery processing.

When you run this command, after-imaging and two-phase commit must be disabled, and the database must be offline; otherwise, RFUTIL returns an error message.

After you change the AI block size, RFUTIL uses the new block size in all database operations.

Use the PROSTRCT STATISTICS qualifier to display the block sizes for a database.

Typically, if you change the AI block size, you should also change the before-image (BI) block and cluster size; otherwise, the increased AI performance will cause a BI bottleneck.

See Managing Performance for more information about using the RFUTIL AIMAGE TRUNCATE utility.