Deallocating resources

Deallocation releases resources allocated to your program. You can dynamically deallocate resources that were allocated either dynamically or through JCL, unless the data set is:

• Open
• A member of an open concatenated group
• A private catalog.

Data sets are unallocated:

• When you explicitly deallocate them
• When they are closed if FREE=CLOSE is specified
• At the end of the job step if not deallocated earlier

When a data set is unallocated:

• You can use the ddname in subsequent dynamic allocation requests.
• The system processes the data set disposition.
• The system frees the unit to which the data set was allocated if it is not being used for any other DD within the step.
• The system releases the volumes on which the data set was allocated if it is not being used for any other DD within the step.
• The data set is DEQed and other jobs can use the data set, except when the:
  • System has deleted it as part of disposition processing (the data set will no longer exits and therefore cannot be referenced by any other jobs).
  • Data set is referenced in the JCL of a later step of this job (the data set is not DEQed until it is unallocated by the last step whose JCL references it).
• Although temporary data sets are never able to be used by other jobs, if the last reference to a temporary data set in the job is PASS, the system releases a:
  • Temporary VIO data set at the end of the last step in which it is referenced
    Note: The system never ENQs VIO data sets.
  • Releases a batch-allocated temporary non-VIO data set at the end of the job.