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: - DFSMShsm does not perform extent reduction on any extended format
sequential data set.
- 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.