There are four types of restarts:

• Automatic step restart
• Automatic checkpoint restart
• Deferred step restart
• Deferred checkpoint restart

Only the automatic restarts retain the information (step completion codes) necessary to perform valid evaluations of any relational expressions based on prior steps.

If you plan to use either type of deferred restart, you should keep certain points in mind when coding the JCL for the job. Planning ahead in this manner can help prevent the need to update the JCL when the job is submitted for restart. The points to consider are the following:

• Relational expressions on IF/THEN statements that refer to a step preceding the restarted step are evaluated as false.
• Relational expressions on IF/THEN statements on steps following the restarted step can still refer to these following steps, but should also check to see whether the referenced steps actually ran during this invocation. The default value for relational expressions on IF/THEN statements is false, which, unlike COND, will cause the system to skip steps. Adding a ¬STEP.RUN condition is recommended. See Example 7 for an example of a statement construct with a deferred checkpoint restart.