Edward Jaffe said:
Thankfully! This deferral is usually very short lived.
But isn't that the problem here? DSLIST data is
obtained via superlocate, which has the potential
of retrieving enormous amounts of data from
multiple catalogs in a single invocation of SVC26.
From: Edward Jaffe <[EMAIL PROTECTED]>
Reply-To: IBM Mainframe Discussion List <IBM-MAIN@BAMA.UA.EDU>
To: IBM-MAIN@BAMA.UA.EDU
Subject: Re: Interrupting DSLIST [resent with the correct Reply To]
Date: Thu, 11 Jan 2007 23:15:54 -0800
Tony Harminc wrote:
Paul Gilmartin wrote:
Why all this mickeymouse? Why doesn't ATTN simply work?
It's partly an ISPF thing; they broke the TSO attention paradigm many
years
ago. Even the most basic use of ATTN doesn't work properly under ISPF;
once
you've hit it, you can't return to the command in progress, as you can if
you started from a READY prompt.
It's completely up to the application. We support ATTN processing in our
ISPF-based products. For example, long-running FIND commands in (E)JES can
be easily stopped by pressing ATTN. (Might need to press it twice if using
a VTAM session manager. But, in that case, our application still only sees
it once.)
Another problem - and a more fundamental one - is that if the serious work
is being done in a system routine (SVC, PC, or system state code),
attention
processing will usually be deferred.
Thankfully! This deferral is usually very short lived.
The real problem is that attention handling in TSO/E is strictly an
application issue. Most system services don't "play the game" and, even if
they wanted to, there isn't any kind of address-space-level indication that
ATTN was pressed (except that which you implement your own). Sure, the
exits get scheduled in an IRB. But how does the code in the exit tell the
application code running in the PRB to "break"? You can set a flag in a
shared data area. But, that's only good if the flag is tested periodically
by the mainline. What if the mainline is not currently running your
application's code? Or what if it's stuck waiting for a resource of some
kind? Any program that doesn't establish and process its own attention
exits has the potential to not recognize when ATTN has been pressed. I'm
afraid that's most programs. :-(
In (E)JES, we implemented a scheme where one ATTN "breaks" (by setting a
flag that is periodically tested) and a second ATTN forces an abend that
forces the TCB into recovery. Works pretty well. But sometimes people get
gratuitous dumps from impatient users.
--
Edward E Jaffe
Phoenix Software International, Inc
5200 W Century Blvd, Suite 800
Los Angeles, CA 90045
310-338-0400 x318
[EMAIL PROTECTED]
http://www.phoenixsoftware.com/
_________________________________________________________________
Your Hotmail address already works to sign into Windows Live Messenger! Get
it now
http://clk.atdmt.com/MSN/go/msnnkwme0020000001msn/direct/01/?href=http://get.live.com/messenger/overview
----------------------------------------------------------------------
For IBM-MAIN subscribe / signoff / archive access instructions,
send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO
Search the archives at http://bama.ua.edu/archives/ibm-main.html
