COMPACTPERCENT: Specifying the percentage of space saved for compaction

Explanation: COMPACTPERCENT(pct) is an optional parameter specifying the percentage of space saved if DFSMShsm compacts all data sets. For pct, substitute a decimal number from 0 to 99 to specify the least amount of space you want saved if DFSMShsm compacts a data set.

If you request compaction, DFSMShsm compacts a data set when it migrates or backs up the data set for the first time. DFSMShsm then compares the number of bytes written to the total bytes of the original data set and computes the percentage of bytes saved. If the percentage saved is not greater than or equal to pct, DFSMShsm does not compact the data set during subsequent migrations or backups. DFSMShsm does not check whether or not the data set was compacted during migration if DFSMShsm is currently backing up the data set. Similarly, DFSMShsm does not check whether or not the data set was compacted during backup if DFSMShsm is currently migrating the data set.

SMS relationship: Parameter differs in meaning when applied to SMS-managed or non-SMS-managed DASD volumes or data sets.

SETSYS default: None.

DFSMShsm default: If you do not specify this parameter on any SETSYS command, the DFSMShsm default is 40.
Note:
  1. DFSMShsm makes this comparison only for cataloged data sets.
  2. DFSMShsm compacts a data set only if it can save at least one track on DASD or the data set migrated to an SDSP data set.
  3. Compaction always occurs during backup processing if SETSYS COMPACTPERCENT(0) is specified and DFSMShsm is to compact the data set.
Parent topic: Optional parameters of the SETSYS command