z/OS MVS JCL Reference
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DUMMY parameter

z/OS MVS JCL Reference

Parameter type

Positional, optional


Use the DUMMY parameter to specify that:
  • No device or external storage space is to be allocated to the data set.
  • No disposition processing is to be performed on the data set.
  • For BSAM and QSAM, no input or output operations are to be performed on the data set.

One use of the DUMMY parameter is in testing a program. When testing is finished and you want input or output operations performed on the data set, replace the DD DUMMY statement with a DD statement that fully defines the data set.

Another use of the DUMMY parameter is in a cataloged or in-stream procedure. Code on the DD DUMMY statement all the required parameters. When the procedure is called, nullify the effects of the DUMMY parameter by coding on the DD statement that overrides the DD DUMMY statement a DSNAME parameter that matches the DSNAME parameter on the DD DUMMY statement. For example, procedure step PS contains the following:
Nullify the DUMMY parameter by coding:
   //JS      EXEC  PROC=PROC1
   //PS.DS1  DD    DSNAME=A

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