When both VOL=REF and UNIT=AFF are specified, VOL=REF processing
takes precedence over UNIT=AFF. The &UNIT read-only variable may
contain blanks or 'AFF= ', depending on the disposition of the referenced
DD.
Recommendation: When specifying both
VOL=REF and UNIT=AFF, ensure that the ACS routines check for &ANYVOL='REF=ST',
'REF=SD' or 'REF=NS' before checking the &UNIT
read-only variable. This ensures that the ACS routines select the
correct classes.
Unlike volume reference processing, in which the storage class
is produced from the REF'ed DD, unit affinity processing allows you
to break the affinity by setting a different storage class. Even though
the AFF'ed DD's storage class is passed as input to the storage class
routine, the storage class routine must set a valid storage class
for the job to run successfully.