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DB2 Manager User Guide 115
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