ISRE775 Panel Display Error / ZSHADOW Length?

[Joe Denison]

I'm getting an intermittent ISRE775 error when scrolling down while using
the VIEW service. I use a modified ISREDD02 panel with a PANEXIT
statement in the panel INIT section for invoking a REXX exit to modify the
ZSHADOW content.

This worked fine in z/OS 1.7 (ISPF 5.7) but on a 1.9 (ISPF 5.9) system,
viewing the exact same data, I'm getting the ISRE775 error
(intermittently, although I can reproduce it).

Using ISPVCALL, not too far above the ISRE775 error, a couple of lines are
displayed as shown on the 1.9 system:

>Msg S:Data truncation occurred TLDMMID=ISPV006
?Msg L:Data for CHAR format variable "ZSHADOW" was too long.

These do not appear on the 1.7 system, although the exact same data is
being displayed with the VIEW service. I don't believe the contents of
the ZSHADOW variable have increased in length within the panel exit (I'm
as certain as can be without testing it, although I suppose anything is
possible.)

Does anyone know definitively if anything has changed within the ISPF
panel display routines or the VIEW service beyond 1.7 that checks the
ZSHADOW content length and invokes the ISRE775 error if this condition
occurs? I'm thinking that possibly the 1.7 ISPF and prior might tolerate
this, but a control was added post-1.7? Or, does the above message
regarding ZSHADOW really indicate an error condition, or is it just
informational?

I'm posting this question because currently I don't have an opportunity to
test this in a debugging mode on the 1.9 system (running compiled REXX
there). Ability to test will come soon but I just wanted to see if anyone
might be in the know so-to-speak on this issue. I have tested the panel
exit on 1.7 and arbitrarily added from a few to a few thousand additional
characters to the ZSHADOW variable contents, but the result was without
any adverse effect.

Thanks to anyone who can help!

--
Joe

[Dave Salt]

Joe,

Prior to z/OS 1.9, panel exits were unable to change the length of variables. That changed in z/OS 1.9. So, is it possible that your panel exit has always changed the length of the shadow variable (perhaps accidentally), but until now the length change was ignored and therefore didn't cause any problems?

Dave Salt

See the new SimpList(tm) rollover image at:
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> Date: Mon, 14 Apr 2008 23:34:59 -0400
> From: j...@JOEDENISON.COM
> Subject: ISRE775 Panel Display Error / ZSHADOW Length?
> To: ISP...@LISTSERV.ND.EDU

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[Joe Denison]

Dave, you were right on target -- accidental change to the ZSHADOW length.
Thanks much for your helpful advice!

I won't pursue this further, but I am curious as to why the length change
would be allowed if it causes an error. I suppose there is a circumstance
where altering the length of ZSHADOW would be useful? I'll save that for a
day when I'm REALLY bored. :-)

--
Joe

[Dave Salt]

Joe, as you know ZSHADOW is a "shadow" for another variable (i.e. ZDATA). As a shadow, it can be less than or equal to the length of the variable it shadows. If you were accidentally changing it to make it longer than the length of ZDATA, this wouldn't have mattered prior to z/OS 1.09 because your attempted length change would have been ignored.

Now that you've moved to z/OS 1.09, panel exits are allowed to change the length of variables. This has nothing to do with ZSHADOW in particular; any variable length can be changed. It is okay to increase or decrease the length of ZSHADOW, providing it never becomes longer than ZDATA. So, your 'accidental' change to ZSHADOW which made it longer than ZDATA is now getting passed back to the panel, which is what caused things to go pear shaped.

So, in summary, yes there are circumstances where it is useful to alter the length of ZSHADOW (e.g. making it shorter than ZDATA or even setting it to null). Just don't attempt to make it longer than ZDATA and you'll be okay.

HTH,

Dave Salt

See the new SimpList(tm) rollover image at:
http://www.mackinney.com/products/SIM/simplist.htm

> Date: Sat, 19 Apr 2008 00:07:55 -0500
> From: j...@JOEDENISON.COM

> Subject: Re: ISRE775 Panel Display Error / ZSHADOW Length?

> To: ISP...@LISTSERV.ND.EDU

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