JCL - REGION Parameter

Coding REGION parameter on a JOB step is different from coding it on a EXEC step.

A JOB statement REGION parameter applies to all steps of the job and overrides any EXEC statement REGION parameters.

When no REGION parameter is on the JOB statement, the system uses an EXEC statement REGION parameter, but only during the job step. Code EXEC statement REGION parameters when you want to specify a different region size for each job step.