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.

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:

   //DS1     DD    DUMMY,DSNAME=A,DISP=OLD

Nullify the DUMMY parameter by coding:

   //JS      EXEC  PROC=PROC1
   //PS.DS1  DD    DSNAME=A