After DFSMShsm performs migration for the non-SMS-managed volumes,
it performs extent reduction. Extent reduction for non-SMS-managed
data sets is performed in the same way as for SMS-managed data sets.
Note: DFSMShsm does not do extent reduction if you have specified
SETSYS TAPEMIGRATION(DIRECT) and you have not specified an ML1 volume.
The extent-reduction process would cause contention between migration
and recall for the target tape ML2 volume.