Determining eligible data sets for extent reduction

After determining if the data set is eligible for backup, DFSMShsm determines if the data set is eligible for extent reduction. DFSMShsm identifies a non-VSAM single-volume data set as eligible for extent reduction if all of the following criteria are met:
  • The data set has as many extents or more than the value specified by the MAXEXTENTS parameter of the SETSYS command.
  • The data set also meets data integrity age.
  • If the data set is an SMS-managed MVS™ or IMS™ GSAM checkpointed data set, it meets the requirements for date-last-referenced plus the number of days the data set is to be treated as unmovable.
  • The value of the COMMAND OR AUTO MIGRATE attribute is BOTH.
Note:
  1. DFSMShsm does not perform extent reduction on any extended format sequential data set.
  2. Extent reduction will not occur on SMS-managed data sets with COMMAND OR AUTO MIGRATE=NONE specified, or on non-SMS-managed data sets with SETMIG NOMIGRATION specified.
Parent topic: Automatic primary space management