Recovering a list of objects

You can recover table spaces, table space partitions, pieces of a nonpartitioned table space, index spaces, index space partitions, and indexes.

When you recover an object to a prior point in time, you should recover a set of referentially related table spaces together to avoid putting any of the table spaces in CHECK-pending status. Use REPORT TABLESPACESET to obtain a table space listing.

Objects that are to be restored from a system-level backup are restored by the main task for the RECOVER utility by invoking DFSMShsm. Objects that are to be restored from a FlashCopy® image copy are restored by invoking DFSMShsm.

Each object can have a different base from which to recover: system-level backup, image copy, concurrent copy, or FlashCopy image copy.

RECOVER does not place dependent table spaces that are related by informational referential constraints into CHECK-pending status.

The RECOVER utility merges incremental copies serially and dynamically. As a result, recovery of a table space list with numerous incremental copies can be time-consuming and operator-intensive.

If referential integrity violations are not an issue, you can run a separate job to recover each table space.

When you specify the PARALLEL keyword, Db2 supports parallelism during the RESTORE phase and performs recovery as follows:

  • During initialization and setup (the UTILINIT recover phase), the utility locates the full and incremental copy information for each object in the list from SYSIBM.SYSCOPY.
  • The utility sorts the list of objects for recovery into lists to be processed in parallel according to the number of tape volumes, file sequence numbers, and sizes of each image copy.
  • The number of objects that can be restored in parallel depends on the maximum number of available tape devices and on how many tape devices the utility requires for the incremental and full image copy data sets. You can control the number of objects that are to be processed in parallel on the PARALLEL keyword. You can control the number of dynamically allocated tape drives on the TAPEUNITS keyword, which is specified with the PARALLEL keyword.
  • If an object in the list requires a Db2 concurrent copy, the utility sorts the object in its own list and processes the list in the main task, while the objects in the other sorted lists are restored in parallel. If the concurrent copies that are to be restored are on tape volumes, the utility uses one tape device and counts it toward the maximum value that is specified for TAPEUNITS.
  • If objects in the list require a system-level backup that was dumped to tape as its recovery base (that is, the FROMDUMP option was specified), the RECOVER utility will invoke DFSMShsm to restore the data sets for the objects in parallel. In this case, the degree of parallelism cannot exceed the maximum number of tasks that can be started by the RECOVER utility. DFSMShsm restores the data sets in parallel based on its installation options.