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What is the difference between the Refer-back & Overriding parameters?
Posted: Fri Jun 17, 2016 2:38 pm
by 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.
Re: What is the difference between the Refer-back & Overriding parameters?
Posted: Fri Jun 17, 2016 3:37 pm
by nicc
I don't know why you asked! Your answer was correct and that demonstrates that they are not the same.
Re: What is the difference between the Refer-back & Overriding parameters?
Posted: Sat Jun 18, 2016 9:10 am
by 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.
Re: What is the difference between the Refer-back & Overriding parameters?
Posted: Sat Jun 18, 2016 4:56 pm
by 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:
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//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.
Re: What is the difference between the Refer-back & Overriding parameters?
Posted: Tue Jun 21, 2016 3:22 pm
by Sushant S
nicc wrote:
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?
Re: What is the difference between the Refer-back & Overriding parameters?
Posted: Tue Jun 21, 2016 4:14 pm
by 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.
Re: What is the difference between the Refer-back & Overriding parameters?
Posted: Thu Jun 23, 2016 3:05 pm
by Sushant S
nicc wrote: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.