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

All sort of Mainframes Interview Questions.
Previous topicNext topic

Topic Author
Sushant S
Registered Member
Posts: 20
Joined: Fri Aug 16, 2013 2:44 pm
Zodiac: Virgo

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

Post by Sushant S » Fri Jun 17, 2016 2:38 pm

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.


Code: Select all

//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
Global Moderator
Global Moderator
Posts: 578
Joined: Wed Apr 23, 2014 8:45 pm

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

Post by nicc » Fri Jun 17, 2016 3:37 pm

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


Regards
Nic


Topic Author
Sushant S
Registered Member
Posts: 20
Joined: Fri Aug 16, 2013 2:44 pm
Zodiac: Virgo

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

Post by Sushant S » Sat Jun 18, 2016 9:10 am

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
Global Moderator
Global Moderator
Posts: 578
Joined: Wed Apr 23, 2014 8:45 pm

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

Post by nicc » Sat Jun 18, 2016 4:56 pm

Take an example:
If this is your catalogued procedure:

Code: Select all

//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)

Code: Select all

//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.


Regards
Nic


Topic Author
Sushant S
Registered Member
Posts: 20
Joined: Fri Aug 16, 2013 2:44 pm
Zodiac: Virgo

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

Post by Sushant S » Tue Jun 21, 2016 3:22 pm

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?




nicc
Global Moderator
Global Moderator
Posts: 578
Joined: Wed Apr 23, 2014 8:45 pm

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

Post by nicc » Tue Jun 21, 2016 4:14 pm

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.


Regards
Nic


Topic Author
Sushant S
Registered Member
Posts: 20
Joined: Fri Aug 16, 2013 2:44 pm
Zodiac: Virgo

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

Post by Sushant S » Thu Jun 23, 2016 3:05 pm

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.



Previous topicNext topic

Return to “Interview Questions.”