Dynamic Allocation and Dynamically Concatenated Data Sets

Checkpoint/restart supports the use of dynamic allocation by problem programs. There are, however, several restrictions with a checkpointed job involving the use of dynamically concatenated data sets. See z/OS MVS Programming: Authorized Assembler Services Guide for information about the specification of dynamically concatenated data sets.

If you code VOL=REF to refer to a nonspecific tape DD request, then after a restart the two DDs may have different volumes from each other. This occurs when the program writes the first data set before the checkpoint, unallocates that data set and does not open the second data set until after the restart.

If a VIO data set is dynamically allocated prior to a checkpoint and unallocated after checkpoint, the step is ineligible for restart until the next checkpoint is taken.

When the checkpointed job requests dynamic concatenation, the following restrictions apply:

On a deferred or automatic checkpoint/restart, JCL-defined DD statements that were dynamically concatenated (by SVC 99) with the permanently concatenated attribute will not be properly resolved. This will result in one or more missing DD statements. If the restart attempt fails, message IEF007I, with reason code 34, will be issued.
On an automatic checkpoint/restart of a job that uses dynamically allocated data sets that had the permanently concatenated attribute, the restart may produce incorrect results. For example, the DDs in the concatenated group may not be matched properly, causing concatenation of the wrong DDs. Restart processing may not detect this type of error. This type of job or step should specify RD=NR in its JOB or EXEC statement. If the job or step fails, it can be resubmitted for a deferred checkpoint/restart.
On either a deferred or automatic checkpoint/restart of a job which uses dynamically concatenated data sets, unit affinity requests for the concatenated DDs may or may not be accepted on the restart. This is true with or without the permanently concatenated attribute.
You cannot use the nocapture option of dynamic allocation.