When data set stacking is
specified using VOL=SER within a job
step, the system ensures that all the data sets making up the data
set collection (a group of data sets intended to be allocated on the
same tape volume or set of tape volumes as a result of data set stacking)
are directed to the same device category. If the ACS routines initially
directed the stacked allocations to different device categories, the
system detects this and reinvokes the ACS routines, passing additional
information to those routines. The ACS routines can then do one of
the following:
- Correct the problem and route the allocations
to consistent device
categories
- Fail the stacked allocation (if the ACS routine
exits with a nonzero
return code)
- Fail to correct the inconsistency, in which case
SMS fails the
allocation
Recommendation: The system
cannot detect data set stacking if VOL=SER is used to stack data sets
across jobs or job steps. In these instances, you can change your
JCL to specify VOL=REF instead of VOL=SER. For more recommendations
on when to use VOL=REF versus VOL=SER for data set stacking, see
z/OS MVS JCL User's Guide.
The system reinvokes the ACS routines only when all of the following
conditions are true:
- The request is part of a data set collection based on a data-set-sequence-number
greater than one specified on the LABEL parameter, and a VOL=SER,
where at least one of the volume serial numbers matches one of the
volume serial numbers for a previous request in the same step.
- The
request is currently directed to a different device category
than the other requests in the data set collection.
- The request
is DISP=NEW (or DISP=MOD treated as NEW).