DSNAME

Getting closer to a JCL one liner equivalent to Unix head -1.

June 14, 2019 Mainframe No comments , , , , , , , ,

I was somewhat bemused by how much JCL it took to do the equivalent of a couple ‘head -1’ commands.  It was pointed out to me that INDATASET, OUTDATASET can be used to eliminate all the DD lines, and that all but the SYSPRINT DDs for IDCAMS were not actually required.  This allows the JCL for these pair of ‘head -1’ commands to be shortened to:

The REPRO lines still have to be split up because of the annoying punch-card derived 72 column restrictions of JCL. Note that to use OUTDATASET in this way, I had to sacrifice the JCL shell variable expansion that I had been using. To retain my shell variables (SET TID=UT; SET CID=UT128) I still need DDNAME statements to do the shell expansion in JCL proper, since that doesn’t occur in the SYSIN specification.  Translated to Unix, we must think of this sort of SYSIN “file” as being single and not double quoted (unlike a Unix <<EOF…EOF inline file where shell script are expanded).  The JCL is left reduced to:

Note that since I opted to retain the DDNAME statements, the REPRO lines are now short enough to each fit on a single line.

It turns out that there’s also a way to do variable expansion within the SYSIN, essentially treating something like a Unix double quoted script variable.  You need to explicitly export the symbols in the JCL prologue using EXPORT SYMLIST, and then import them in the SYSIN specification using SYMBOLS=CNVTSYS

I’ve switched to IDS and ODS to make the lines shorter, which makes it possible for one of the REPRO lines to be a one liner (with 6 lines of helper code).  The final JCL line count weighs in at 8:2 vs. Unix, but is not as bad as the original JCL I constructed (22 lines.)

VSAM creation and population with JCL and IDCAMS

March 7, 2017 Mainframe No comments , , , , , , , ,

I learned a few JCL DATASET related things yesterday that seemed notable, at least for a JCL newbie.

Delete a DATASET, and ignore any error.

Each time I’ve wanted a DATASET cleanup step in JCL I’ve been using a separate script, and running that first.  A better way of doing this is to include a IDCAMS job step in the script, and have that do the deletion

//CLEANUP EXEC PGM=IDCAMS
//SYSIN DD *
  DELETE PJOOT.XXXXX005
  SET MAXCC = 0
/*
//SYSPRINT DD SYSOUT=*
//SYSOUT   DD SYSOUT=*
//*SYSTERM  DD SYSOUT=*

This deletes the file PJOOT.XXXXX005, which in this case was a VSAM file. In case that file (a DATASETs in mainframe-eze) did not exist, the error code for that DELETE is ignored by setting MAXCC=0. If you have multiple things that you want to do with IDCAMS, you can do things like DELETE and then ALLOCATE immediately, such as

//REALLOC EXEC PGM=IDCAMS
//SYSIN DD *
  DELETE PJOOT.XXXXX005
  SET MAXCC = 0
  DEFINE CLUSTER (NAME(PJOOT.XXXXX005) -
               CYLINDERS(1) VOLUMES(LZ0000) -
               INDEXED -
               KEYS(4 0) -
               RECORDSIZE(240 240) -
               ) -
         DATA (NAME(PJOOT.XXXXX005.DATA)) -
         INDEX (NAME(PJOOT.XXXXX005.INDEX))
/*
//SYSPRINT DD SYSOUT=*
//SYSOUT   DD SYSOUT=*
//*SYSTERM  DD SYSOUT=*

This does the DELETE, ignores any error, and then proceeds to do the new ALLOCATE for the VSAM file. I haven’t seen any way described of ALLOCATING a VSAM file other than using IDCAMS, except in 3270 screens. I think I’ve seen that LzLabs has 3270 capabilities for this sort of stuff, but I’m not inclined to try to figure out how to use it. I’d rather use our much more intuitive GUI or do it in script with JCL like this.

Copy a DATASET.

Here is some JCL to copy an (INLINE) dataset into the VSAM file created above

//COPY2VS EXEC PGM=IDCAMS
//TARGET DD DSN=PJOOT.XXXXX005,DISP=(OLD,KEEP,KEEP)
//INLINEDD DD DATA,DCB=(BLKSIZE=240,LRECL=240,RECFM=F)
a
brown
fox
quick
/*
//SYSIN DD *
REPRO -
  INFILE(INLINEDD) -
  OUTFILE(TARGET)
/*
//SYSPRINT DD SYSOUT=*
//SYSOUT   DD SYSOUT=*
//SYSTERM  DD SYSOUT=*

There are two quirks that are noteworthy here.

  1. The VSAM file requires the input be sorted, which is why the words from ‘a quick brown fox’ are in the explicitly sorted order above.
  2. The VSAM file was created with RECORDSIZE 240, so the input file had to be forced to LRECL=240 to match.

Omission of either sort or the LRECL matching causes the VSAM load to fail.

This was the first time that I’d seen this specific INLINE DD syntax, with explicit parameters.  The way I’d seen it before was how SYSIN was specified above with ‘NAME DD *’, ending with C “comment start” /* sequence.  It turns out the default end of file delimiter can also be specified, for example, this also works:

//INLINEDD DD DATA,DLM=@@,DCB=(BLKSIZE=240,LRECL=240,RECFM=F)
a
brown
fox
quick
@@

Cat a file to spool

Because IDCAMS can copy files, this can also be used to cat a file to SPOOL if desired.  Here’s an example:

//CATVS JOB
//CATVS EXEC PGM=IDCAMS
//TARGET DD DSN=PJOOT.XXXXX005,DISP=(OLD,KEEP,KEEP)
//SYSIN DD *
REPRO -
  INFILE(TARGET) -
  OUTFILE(SYSOUT)
/*
//SYSPRINT DD SYSOUT=*
//SYSOUT   DD SYSOUT=*
//SYSTERM  DD SYSOUT=*

If I include a step like this, I’m able to see the file contents in our nice GUI spool browser along with the JCL script and all the other output.