Location in the JCL

Most DD statements define data sets to be used in a job step, in a cataloged procedure step, or in an in-stream procedure step; these appear after the EXEC statement for the step. Some DD statements define data sets for the job, for example, the JOBLIB DD statement; these appear after the JOB statement and before the first EXEC statement.

When overriding or adding to procedures: Place DD statements that override, nullify, or add parameters immediately following the EXEC statement that calls the procedure. Place overriding and nullifying DD statements first, followed by all added DD statements. Last in the calling step are any DD * or DD DATA statements with their in-stream data.

To override more than one DD statement in a procedure, place the overriding DD statements in the same order as the overridden DD statements in the procedure.