StorageTek 312564001 manual DB2 management processing, Database backup and recovery

Rows which have a high likelihood of being updated after archival may cause a significant amount of archival and re-archival processing. A table containing rows which are likely to be updated in this manner are not suitable for migration using DB2 Manager.

DB2 Manager does not impose limitations on the way in which rows are referenced from a DB2 application program. Every possible means of accessing a migrated row via SQL commands is supported, including joins and unions.

Multiple migrated and un-migrated rows from one or more tables may be accessed via a single SQL command from a DB2 application program. However, if a large number of migrated rows is referenced by execution of such a command, then it may take a substantial length of time for execution of that command to be completed if migrated rows are not resident on Archive Manager disk storage. Table migration via DB2 Manager may not be appropriate if retrieval requests of this nature are likely to be performed on a frequent basis.

Alternatively, in these circumstances replacement of a single SQL command via a row-by-row operation using DB2 cursor processing will give a program control over the number of retrievals of migrated rows which may be required to complete an operation – in this case there will be a one-for-one relationship between a single FETCH command and a single migrated row retrieval operation.

DB2 management processing

Database backup and recovery

There is no change required to backup and recovery processing procedures for tablespaces containing tables which have been enabled for DB2 Manager migration. Image copies should be taken normally as for non-enabled tables. However, as the size of the tablespaces used for storage of tables may now have been substantially reduced, the length of time taken for image- copy processing will be reduced by a corresponding amount.

Restore of a tablespace containing a migration-enabled table is performed in an identical manner to that of a tablespace containing a non-enabled table. DB2 will restore the 18-byte stubs containing information about migrated rows, as well as restoring non-migrated rows, to the condition they were in at the time the image-copy was taken. The stubs contain all the information necessary to access migrated rows from Archive Manager.

Database reorganization

Tables which have been enabled for migration processing must be defined in a partitioned tablespace. This tablespace will have one partition for

DB2 Manager User Guide	15
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