Overriding parameters is a technique that allows you to replace the coded parameter values temporarily. This technique is mainly used to replace the parameter values coded in the PROC from the calling JCL. This way, we can modify all parameter values without changing the actual PROC.

The overriding parameters can be coded with the EXEC statement at the step level. This is useful when running the same job with different input or output datasets without changing the PROC.

Overriding parameter can be done in 3 ways -

• Replacing existing parameter.
• Adding new parameter.
• Nullifying parameters.

Replacing existing parameter -

This overriding type replaces the existing parameter, which is already coded in PROC.

Syntax -

//STEPname EXEC proc-name
//STEPname.DDname   DD modifying-parameter1,modifying-parameter2,..

//PROC   proc-name

Example -

PROC - Let us assume the PROC is calling in all steps.

//MTHPROC PROC
//STEP01  EXEC PGM=PROG1,COND=EVEN
//STEPLIB DD   DSN=MATEPK.COBOL.LOADLIB,DISP=SHR
//INPUT   DD   DSN=MATEPK.INPUT.OLDPS,DISP=SHR

PROG1 runs using MATEPK.INPUT.NEWPS as input.

Scenario1 - Overriding dataset.

JCL -

//STEPPR  EXEC MTHPROC
//STEP01.INPUT   DD   DSN=MATEPK.INPUT.NEWPS,DISP=SHR

Scenario2 - Overriding STEPLIB.

JCL -

//STEPPR  EXEC MTHPROC
//STEP01.STEPLIB   DD   DSN=MATEPK.COBOL.LOADLIB1,DISP=SHR

Scenario3 - Overriding Program name.

JCL -

//STEPPR  EXEC MTHPROC,PGM=PROG2

Scenario4 - Overriding COND.

JCL -

//STEPPR  EXEC MTHPROC,COND=ONLY

Adding new parameter -

This type of overriding adds the parameter to the DD statement that is not already coded in PROC.

Syntax -

//STEPname EXEC proc-name
//STEPname.DDname   DD new-parameter1,new-parameter2,..

//PROC   proc-name

Example -

Scenario1 - Adding new DSNTYPE.

JCL -

//STEP01  EXEC PROC=MTHPROC
//STEP01.INPUT   DD   DSNTYPE=LARGE

PROC -

//MTHPROC PROC
//STEP01  EXEC PGM=PROG1
//INPUT   DD DSN=MATEPK.IEFBR14.PSFILE,                  
//           DISP=(NEW,CATLG,DELETE),                    
//           SPACE=(TRK,(3,2),RLSE),                     
//           UNIT=SYSDA,VOLUME=SER=DEVHD4,               
//           DCB=(DSORG=PS,RECFM=FB,LRECL=80,BLKSIZE=800)

MATEPK.IEFBR14.PSFILE creates with DSNTYPE parameter which is not coded in PROC.

Scenario2 - Adding COND parameter.

JCL -

//STEPPR  EXEC MTHPROC,COND=ONLY

Nullifying parameters -

This type of overriding deletes the existing parameter that is already coded in PROC.

Syntax -

//STEPname EXEC proc-name
//STEPname.DDname   DD parameter1,parameter2,..

//PROC   proc-name

Example -

Scenario 1 -Nullify DSNTYPE.

JCL -

//STEP01  EXEC PROC=MTHPROC
//STEP01.INPUT   DD  DSNTYPE= 

PROC -

//MTHPROC PROC
//STEP01  EXEC PGM=PROG1
//INPUT   DD DSN=MATEPK.IEFBR14.PSFILE,                  
//           DISP=(NEW,CATLG,DELETE),                    
//           SPACE=(TRK,(3,2),RLSE),                     
//           UNIT=SYSDA,VOLUME=SER=DEVHD4,               
//           DCB=(DSORG=PS,RECFM=FB,LRECL=80,BLKSIZE=800),
//           DSNTYPE=LARGE

MATEPK.IEFBR14.PSFILE creates with DSNTYPE parameter as empty.