Then the not-yet-available examples ought to include all the error recovery 
infrastructure needed to assure the least system impact possible.

Like the brief discussions I had with others on this list a few years back 
about code to set the DUCT TRAP fields so that TRAP and COMPARE-AND-TRAP 
instructions would work as architected.  IIRC, the conversation went something 
like this:

"Use PC-ss with a server address space that schedules an SRB in your address 
space to do that, but really, really don't do that because there's no system 
support for it."
"When will there be system support for it?"
"What's the business justification for expending those scarce resources?"
Etc., etc.

An example that showed how to safely set and unset the DUCT TRAP fields with 
all the attendant recovery infrastructure needed would be a lovely, practical 
example to have available.  Not that I'm holding my breath waiting for it to 
appear.

This set of knowledge isn't unknowable, only obscure and esoteric.  IMHO, just 
hiding it doesn't serve the community or the employers who pay us.

Why does there always have to be profit in spreading knowledge?

But I have always known that I am a cockeyed optimist about the free 
availability of knowledge, so I already know the answer to that question even 
if I don't like it much.

Peter

-----Original Message-----
From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf 
Of Binyamin Dissen
Sent: Monday, November 12, 2018 5:54 PM
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: Re: Why are sophisticated system-level coding examples not available? 
[was: RE: Recommended method for accessing secondary access spaces]

There are a large number of parts to make sure that things are done the right
way, and that a fault will not bring the system to a crash.

While one might be able to show examples of simple techniques, there is a lot
of infrastructure required to handle problems.

For example, what happens if you force an SSAR to a swapable address space
that happens to be swapped in and the address space gets swapped out in the
middle? If I recall correctly, the next page fault that I had in the target
address space caused a MEMTERM of the home address space - which meant no
ESTAEs got control.



On Mon, 12 Nov 2018 22:11:15 +0000 "Farley, Peter x23353"
<peter.far...@broadridge.com> wrote:

:>And that was my whole point -- Where are the examples for programmers to see 
how to do it the right way?
:>
:>If SHARE has some presentations it is good to know that.  Not the easiest 
place to search for stuff, but at least it is accessible.
:>
:>Yes, of course experience is the best teacher, but without even examples of 
how to do something it is awfully hard to figure it out on your own.
:>
:>". . . thoroughly knowledgeable about how the system works" is a whole 
'nother can of worms.  Back in the day places like universities in some cities 
offered "adult education" courses on MVS debugging and internals.  I took a 
two-semester course like that back around the time that the MVS lock manager 
was first introduced, and it was wonderful, complex, interesting material to 
learn.
:>
:>Of course, all that is ancient history now.  No university or education 
center offers anything like that anymore.  Much more profitable to offer 
certification courses in Windows.
:>
:>Peter

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