StorageTek 312564001 manual DB2 Manager User Guide, StorageTek Proprietary

utility should not be permitted, by letting the data retention period default to zero values when defining the Archive Manager database. Refer to “Define Archive Manager databases” on page 27 for information on this issue.

The database maintenance procedure should be performed at regular intervals for each Archive Manager database used for storage of migrated rows by DB2 Manager, in order to recover unused space from within the database which has been freed due to object deletion. The frequency at which the procedure needs to be performed will depend on the rate of object deletion, and the level of requirement for reclaiming tapes from the database in order to replenish scratch pools. The rate of object deletion, in turn, is governed by the frequency of deletion of migrated rows, either through explicit SQL DELETE request, SQL UPDATE requests, or restore of migrated rows from Archive Manager to DB2 via the row restore utility OTDBP120.

Control of the tape recycling process for an Archive Manager database is via the ‘recycle threshold’ entry set during the database definition process (see “Define Archive Manager databases” on page 27). This process must be executed for each DB2 table to be processed by DB2 Manager.

The recycle threshold specifies a numeric value in the range 00-99, which represents a percentage of active objects for any volume in the database. A tape volume becomes eligible for recycling by the Archive Manager database maintenance utility if the level of active objects on that volume falls below this threshold. If this entry is omitted during the database definition process, a default value of ‘0’ is used; this indicates that no recycling is to be performed on this database.

When a tape volume becomes eligible for recycling, the Archive Manager database maintenance utility will write all active objects contained within it to a new tape volume at the end of the database. The recycled volume will then be released from the database and may be returned to the appropriate scratch pool.

If the ‘autouncat during recycle’ entry has been set during the database definition process, released volumes will be automatically uncataloged after being released from the database. This facility may be used in conjunction with an installed tape management system to automatically return uncataloged volumes to the correct scratch pool.

The Archive Manager database maintenance utility processes a single Archive Manager database for each execution. Any tape volume being used by the database maintenance utility will be unavailable for allocation for row migration or migrated row access processing. It is recommended therefore that database maintenance for an Archive Manager database be scheduled for execution when there is no row recall or migration activity for the DB2 table associated with that Archive Manager database. It is not necessary to terminate the DB2 Manager control region while Archive Manager database maintenance is being performed.

An Archive Manager database’s recycle threshold may be altered at any time, via the supplied Archive Manager database administration dialogs. Note also that where multiple storage levels are in use for an Archive Manager

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