How to improve RECOVER performance

You can improve the performance of the RECOVER utility by taking certain actions.

To improve recovery time, consider recovering to a quiesce point or SHRLEVEL REFERENCE copy instead of recovering to any point in time. The following factors impact performance when you recover to a non quiesce point:

  • The duration of the units of recovery that were active at the recovery point.
  • The number of Db2 members that have active units of recovery to roll back.

Use MERGECOPY to merge your table space image copies before recovering the table space. If you do not merge your image copies, RECOVER automatically merges them. If RECOVER cannot allocate all the incremental image copy data sets when it merges the image copies, RECOVER uses the log instead.

Include a list of table spaces and indexes in your RECOVER utility statement to apply logs in a single scan of the logs.

If you use RECOVER TOCOPY for full image copies, you can improve performance by using data compression. The improvement is proportional to the degree of compression.

Consider specifying the PARALLEL keyword to restore image copies from disk or tape to a list of objects in parallel.

If you are recovering concurrent copies, consider specifying the CURRENTCOPYONLY option to improve performance. When you specify this option, RECOVER can issue one DFSMSdss RESTORE command for multiple objects. The utility issues one RESTORE command for each group of objects that is associated with the concurrent copy data set. If you do not use the CURRENTCOPYONLY keyword, RECOVER issues one RESTORE command for each object.

If you are recovering an object from a system-level backup, RECOVER invokes DFSMShsm, which controls parallelism. If the system-level backup resides on disk, the RECOVER utility passes the object to DFSMShsm before processing the objects to be restored from image copies or concurrent copies. If the system-level backup resides on tape, the RECOVER utility processes the objects to be restored from system-level backups, image copies, and concurrent copies at the same time.

Recovery from a FlashCopy® image copy with consistency or from a sequential image copy with consistency might take longer due to the additional processing required to read the logs and apply any changes made after the point of consistency.