JCL Requirements and Restrictions on Deferred Step Restart

To perform a deferred step restart, you must provide the data set environment required by the restart job. This can be accomplished by using the conditional disposition subparameter in the appropriate DD statements during the original execution of the job. Conditional dispositions in the original job must be used to:

Delete all NEW data sets used by the step to be restarted.
Catalog all data sets passed from steps preceding the restart step, to the restart step, or to steps following the restart step. Abnormal termination of the restart step, when it is originally run, causes cataloging of the passed data sets. The information is available to the following steps when the job is resubmitted.
Keep all OLD data sets used by the restart step, other than those passed to the step.

If a data set with DISP=MOD on tape is used in the restart step, the data set is not repositioned at the start of the restart execution, and data written into it during the restart execution follows the data written during the original execution. You may want to reposition the data set after restart so the data written during the restart execution overlays the data written during the original execution. Any data sets that are dynamically deallocated have the disposition specified at the time deallocation occurred. Conditional disposition processing is not done during abend.

The following rules apply to the restart job:

Code the RESTART parameter on the JOB statement.
If data sets are passed from steps preceding the restart step to the restart step or to steps following the restart step, the DD statements receiving the data sets must entirely define the data sets. They must explicitly specify volume serial number, device type, data set sequence number, and label type, unless this information can be retrieved from the catalog. It is recommended that passed data sets be conditionally cataloged during abnormal termination of the original execution. Label type cannot be retrieved from the catalog.
Generation data sets created and cataloged in steps preceding the restart step must not be referred to in the restart step or in steps following the restart step by the relative generation numbers used to create them. They must be referred to by their actual relative generation numbers. For example, a data set created as the +1 data set must be referred to as the 0 data set (assuming that the +2 data set was not also created).
The EXEC statement PGM and COND parameters and the DD statement VOL=REF parameter must not be used in the restart step or in steps following the restart step if they contain values of the form stepname or stepname.procstepname, referring to a step preceding the restart step.