RESTART parameter
A JOB statement parameter that starts a job from a named step, skipping the steps before it.
Also written RESTART=, step restart, restart from a step, checkpoint restart
When a long job fails in step 6, you usually do not want to run steps 1 to 5 again. RESTART on the JOB statement lets you start from the step you name, for example RESTART=STEP06. For a step inside a PROC, you give both names, as in RESTART=STEP06.SORT.
The earlier steps are skipped completely, so anything the restarted step needs from them must still exist. Temporary datasets from the first run are gone. Generation data groups need care: a generation created in the first run as (+1) is now (0), so JCL that creates (+1) again may make an extra generation. Sites often have rules, or scheduler features, for exactly this.
Conditions also change. A step that checks the return code of a skipped step behaves as if that step did not run.
In production, restarts are usually done through the batch scheduler, following the instructions written for that job. Restarting from the wrong step, or without fixing the cause first, can process data twice, so check the runbook before you restart anything.
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- JOB statementThe first statement in every job, giving it a name and telling the system who is running it and how to treat it.
- Job stepOne program execution within a job. A job is simply a sequence of steps that run in order.
- Generation data groupA set of datasets holding successive versions of the same file, so today's copy, yesterday's and last week's all exist under one name.
- Batch schedulerSoftware that submits production jobs automatically in the right order, at the right time, based on what has already succeeded.
- Production supportKeeping live systems running: diagnosing failures, fixing what broke, and getting the service back.
- Temporary datasetA dataset that exists only while one job runs and is deleted automatically when the job ends.