IBM Mainframe Discussion List <[email protected]> wrote on 01/19/2006
06:14:28 PM:
> In <[EMAIL PROTECTED]>, on 01/18/2006
> at 11:53 PM, Paul Gilmartin <[EMAIL PROTECTED]> said:
>
> >WTF SJF?
>
> Scheduler JCL Facility was introduced in MVS/SP 1.3 to support the
> OUTPUT statement. It allowed adding new JCL statements and new
> keywords on existing statements.
>
> >I have heard tales that the JCL C/I is FUBAR ("Beyond Ability to
> >Repair"), and development is afraid to replace or significantly
> >modify it.
>
> I'm not sure that I believe it. certainly the code in the old R/I was
> cleaner than, e.g., the Initiator. Take IEFZGST1 and IEFZGST2 -
> please!
>
The JCL Converter was rewritten in SP4.1.0 (around 1990) as part
of the project to add the //IF THEN ELSE stuff to JCL. I had
no difficulty making a (very minor) modification to it in z/OS 1.7
to specify a LOC parameter on the GETMAIN for the BSAM buffers
for reading JCLLIBs/PROCLIBs, so that these buffers would no longer
need to be pagefixed below 16MB in real storage during I/O
(which of course was simply an oversight in SP4.1.0, but at times
became externally noticeable under some circumstances on one of our
large test systems).
At least some of the interpreter is still very old
assembler code, written in a style which I would guess was related
to storage and performance constraints of a prior era in computing.
I have found that code to be rather challenging to read. While I
don't know that I would characterize it as "fear", I do not relish
the effort it might require for me to understand that code
sufficiently to replace or significantly some parts of it.
On the other hand, it does get modified when necessary, and even I
(although I generally prefer coding in PL/X over assembler)
managed to make a small modification to change the behaviour when
MEMLIMIT was specified for a job which executed on a system running
in ESA/390 mode, in response to an issue that was raised some years
ago on IBM-MAIN.
Jim Mulder z/OS System Test IBM Corp. Poughkeepsie, NY
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