DUMPTMAX parameter

Maximum CCATEMP usage for DUMP

Summary

Default value

0

Parameter type

System

Where set

System manager resettable

Related products

Fast/Backup

Introduced

Before Sirius Mods 6.7

Description

This parameter sets the maximum number of CCATEMP pages any individual DUMP can use.

If a thread is performing an update on a file that is being dumped, and the thread needs to update a page that has not been dumped yet, that page needs to be dumped before the page can be updated. Normally, Fast/Backup will dump such a page almost immediately, and there will be no noticeable delay for the updating transaction. However, if Fast/Backup is waiting for a tape volume switch, perhaps waiting for a tape mount, an updating transaction in this scenario would also have to wait for the tape mount. The result is not good for the updating request and potentially not good for other users in the Online, as resources held by the updating user are not released and, if sub-transaction checkpoints are being used, checkpoints are timed out.

In such a situation, Fast/Backup will try to copy the page to be updated to CCATEMP, allowing the updating thread to continue with its update. After the tape mount is satisfied, the page is copied from CCATEMP, and the CCATEMP used by the cached page is freed. Obviously, if there is a lot of updating for a file being dumped, and the dump ends up waiting on a tape mount, this could result in a lot of CCATEMP being used, leaving insufficient CCATEMP for other applications.

The DUMPTMAX parameter indicates the maximum number of CCATEMP pages that an individual DUMP will be allowed to use to cache pages that are about to be updated. If this number of pages is exceeded in the scenario described above, the updating thread will have to wait for the tape mount, or the dump will be terminated with an error, depending on the setting of the DUMPOPTS parameter.

The default value for DUMPTMAX of 0 means that no limit is placed on the use of CCATEMP pages by Fast/Backup.

See also DUMPTMIN.