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Reading selected volumes of a multi-volume tape file

 
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RickBig

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Joined: 11 Jul 2016
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Location: Canada

PostPosted: Wed Jul 13, 2016 7:26 pm    Post subject: Reading selected volumes of a multi-volume tape file
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We have a (very) old series of batch jobs that read selected volumes of a multi-volume tape file. This is just a technique for splitting the file into 'manageable' segments.

So the code is like:

Code:
//COPY01   EXEC  PGM=SORT                                         
//*                                                               
//SORTIN    DD  DISP=SHR,DSN=MY.BIG.TAPE.FILE,
//          UNIT=TAPE,VOL=SER=(UC4622,UI0455)   


Now until recently, this has been working fine, the step would only read the first two volumes.

Recently however, we see the following on the job output:

Code:
IEC716I SORTIN  :TAPE MULTIVOLUME LIST CORRECTED   


and instead of just the first two volumes being read, the entire file is read. Notably, if the volumes listed do not include the first volume, only the volumes in the scope of the VOL=SER are read.

Our systems people have not explained what caused this to change. Any ideas?

BTW, bypassing label processing, OPTCD=B, resolves the issue.
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Nic Clouston

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PostPosted: Wed Jul 13, 2016 7:52 pm    Post subject:
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No idea but...DISP=SHR for tape is "invalid". You cannot share a tape volume - you should use OLD.
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Robert Sample

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PostPosted: Wed Jul 13, 2016 8:16 pm    Post subject:
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Quote:
BTW, bypassing label processing, OPTCD=B, resolves the issue.
Actually, LABEL=BLP is the DCB subparameter to bypass label processing. What you are doing, from the JCL Reference manual, is:
Quote:
B
requests that the end-of-volume (EOV) routine disregard the end-of-file (EOF) recognition for magnetic tape. For an input data set on a standard-labeled (SL or AL) tape, the EOV routine treats EOF labels as EOV labels until the volume serial list is exhausted. This option allows SL or AL tapes to be read out of volume sequence or to be concatenated to another tape with the same data set name using one DD statement. See "Data Sets that Span Libraries" in z/OS MVS JCL User's Guide for a description of allocation processing for multi-volume data sets created in different tape libraries.
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steve-myers

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PostPosted: Wed Jul 13, 2016 8:30 pm    Post subject:
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Nic Clouston wrote:
No idea but...DISP=SHR for tape is "invalid". You cannot share a tape volume - you should use OLD.
You are correct when you say two jobs cannot "share" a tape volume, but what DISP=SHR is saying is another job can "share" the data set name.

Actually, two jobs can "share" a tape volume, but only one job at a time can have a data set open on the volume. For that matter, one job cannot have 2 (or more) data sets open on one volume at a time. In other words, this won't work -
Code:
//A       EXEC PGM=SORT
//SYSOUT   DD  SYSOUT=*
//SORTIN01 DD  DISP=SHR,LABEL=1,UNIT=TAPE,VOL=SER=TAPEV1,DSN=TAPEV1.FILE1
//SORTIN02 DD  DISP=SHR,LABEL=2,UNIT=TAPE,VOL=SER=TAPEV1,DSN=TAPEV1.FILE2
//SORTOUT  DD  ...
//SYSIN    DD  *
 MERGE ...
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RickBig

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Joined: 11 Jul 2016
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Location: Canada

PostPosted: Thu Jul 14, 2016 1:13 am    Post subject: Reply to: Reading selected volumes of a multi-volume tape file
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Thanks for the valuable feedback. I'm still mystified, however, that the same job would work one way one month, and then differently the next.

I'm unaware of any system changes in the interim (at least I wasn't told of any). Perhaps a PTF was applied...

I'll forward any answer I receive from our support group.
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Bryan Lehner

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PostPosted: Sat Aug 13, 2016 12:03 am    Post subject:
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I experienced this same situation, and a new version of CA-1 had been installed that leveraged the IBM Label Anomaly Exit. We had to start using the OPTCD=B for jobs that read individual tapes of a multi-volume group.
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RickBig

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Location: Canada

PostPosted: Mon Aug 22, 2016 8:01 pm    Post subject: Reply to: Reading selected volumes of a multi-volume tape file
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Thanks, I will check and see if we had a similar update to CA-1 in that time period.
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