Implications of moving data sets after a system-level backup

When you recover data sets from a system-level backup to a prior point in time, the data sets do not need to reside on the same volume as when the backup was made. The RECOVER utility can use system-level backups even if a data set has moved since the backup was created.

You can still recover the objects if you have an object-level backup such as an image copy or concurrent copy. Take object-level backups to augment system-level backups, or take new system-level backups whenever a data set is moved.

You can force the RECOVER utility to ignore system-level backups and use the latest applicable object-level backup by setting the SYSTEM-LEVEL-BACKUPS parameter on installation panel DSNTIP6 to NO. This subsystem parameter can be updated online.

Activities that can affect the ability to recover an object to a prior point in time from a system-level backup include:

  • Migrating to new disk storage or redistributing data sets for performance reasons

    The movement of data sets for disk management should be restricted or limited when system-level backups are taken. When movement of data sets does occur, a new system-level backup or object-level backup should immediately be taken.

  • Using the DFSMShsm migrate and recall feature

    Do not use the DFSMShsm migrate and recall feature if you take system-level backups.

  • Using REORG TABLESPACE or LOAD REPLACE

    To minimize the impact of REORG TABLESPACE and LOAD REPLACE on recoverability, you should always take an inline copy of the underlying table space. You can then use this copy to recover at the object level.

  • Using REORG INDEX or REBUILD INDEX

    If a REORG INDEX or REBUILD INDEX is preventing the use of the system-level backup during recovery of an index, you can use the REBUILD INDEX utility to rebuild rather than recover the index.

  • Using RECOVER from an image copy or concurrent copy

Consider the following restrictions when planning your backup strategy:

  • Data sets can move within a single volume, for example because the volume has been defragmented. In this case, the ability to restore the data is not affected. Recovery of data is not affected if the data set is extended to another volume after it has been copied.

    In the case where the data set originally spanned multiple volumes, the data set would need to be reallocated with extents on each of the same volumes before it could be recovered successfully. The amount of space for the data set extents at the time of the backup can differ from the amount of space that is available at recovery time.

  • The movement of one data set in a system-level backup does not prevent the object-level recovery of other objects from the backup.
  • The movement of data sets does not prevent the use of the RESTORE SYSTEM utility.