What is the difference between the Refer-back & Overriding parameters?

[Sushant S]

Hi,


This was the question which goes like this, what is the difference between the refer-back & overriding parameters? Are not they serving the same purpose? How are they coded in a JCL?

I have answered it like... when we use refer-back, we actually refer back to an earlier DD statement in the job or in cataloged or in in-stream procedure called by a job step.

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//MYJOB JOB ..
//STEP1 EXEC ..
//DD1 DD DSN=REPORT ...
.
.
//DD4 DD DSN=*.DD1

For Over riding, for a JCL in in-stream or Cataloged procedures, the DD names mentioned in the JCL will override the
ones in the procedures.

But I was not able to answer of they behave just the same, do they? Please help.

[nicc]

I don't know why you asked! Your answer was correct and that demonstrates that they are not the same.

[Sushant S]

Becasue I felt that I was not able to answer of they behave just the same, do they? How would I answer it better as I found interviewer was not satisfied with the answer.

[nicc]

Take an example:
If this is your catalogued procedure:

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//COPY PROC IN=,
//          OUT=
//*
//S010    EXEC PGM=IEBGENER
//SYSPRINT DD SYSOUT=*
//SYSUT1   DD DSN=&IN,DISP=SHR
//SYSUT2   DD DSN=&OUT,DCB=*.SYSUT1,
//            SPACE=(TRK,(15,15),RLSE)
//            DISP=(,CATLG,DELETE)
//SYSIN    DD DUMMY

You would normally run it like this (perhaps)

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//NICC JOB (),....
//A EXEC MYPROC,
//  IN=input.dataset.name,
//  OUT=output.dataset.name

But then you want to maximise the space utilisation and the input dataset is LRECL=80, BLKSIZE=800 (really inefficient) so you need an override:

Code: Select all

//NICC JOB (),....
//A EXEC MYPROC,
//  IN=input.dataset.name,
//  OUT=output.dataset.name
//S010.SYSUT2 DD DCB=BLKSIZE=0

However, now-a-days, we have the ISPF so using a refer-back is, more or less, simply laziness on the part of the coder.

[Sushant S]

However, now-a-days, we have the ISPF so using a refer-back is, more or less, simply laziness on the part of the coder.

Thanks for the example. How does ISPF changes that? Sorry but I did not get it. Can you please explain again?

[nicc]

Because in the old days you had to code it all by hand and then punch it onto punch cards so using a refer-back saved effort. With ISPF and online submission you have a good editor that you can use to copy lines and edit as required with next to no effort so such short-cuts are no longer required except by the very lazy.

[Sushant S]

Because in the old days you had to code it all by hand and then punch it onto punch cards so using a refer-back saved effort. With ISPF and online submission you have a good editor that you can use to copy lines and edit as required with next to no effort so such short-cuts are no longer required except by the very lazy.

Thanks nicc.