Recovering DB2 databases

The recoverable structure of data in DB2 is the table space. To ensure recoverability, make an image copy when creating each table space in the OAM configuration database and all the table spaces in each of the object storage databases. Your installation determines how often to make backup copies, based on the usage of each table space. Use this original image copy as a base, and make subsequent periodic incremental image copies of each table space.

At specified intervals (best defined based on the usage of each table space), perform a MERGECOPY on the base (original, full-image copy) and subsequent incremental-image copies to establish a new base. After creating the new base level, perform subsequent incremental image copies in relation to this new base.

The main benefit of periodically using MERGECOPY to create a new base is the time savings at the time of the failure. Merge copies can be time-consuming, so it is best to do them on a timely, convenient basis.

To recover a table space, merge the contents of the DB2 recovery log with the most recent full-image copy of the table space. Because each change made to the database is recorded in the DB2 recovery log, the merge restores the table space to its last point of consistency prior to system failure.

Note:

In DB2, point of consistency is a term that designates a time when all recoverable data accessed by an application program is consistent with other data. It is also known as syncpoint or commit point.
The entries within the DB2 collection name table are synchronized with a corresponding collection name entry in the catalog. Therefore, recovery of the DB2 collection name table must result in a table consistent with the catalog.
If any action is taken that permanently removes an entry from the DB2 collection name table, the corresponding entry must be deleted from the catalog. After a collection entry is removed from the DB2 collection name table and the catalog, objects contained within the collection are no longer accessible or managed by OSMC.

For directions regarding how to make these image copies, see the topic "Plans for backup and recovery" in the IBM Information Management Software for z/OS Solutions Information Center.