On Jan 6, 2008, at 9:26 AM, J R wrote:
Instead of paying for it though I'd rather it be an open source
document or a Wiki.
Many of us on this list make our livings as ISVs, largely based on
knowledge accrued over many decades. While offering assistance
and tidbits of information and know-how is the nature of the beast,
you are asking these people for the keys to their kingdom.
Scraps are free, but what you are asking for is a full-blown product.
This comes at a price whether it be for a complete off-the-shelf
solution, bespoke design and development, education or books
and documentation.
If Binyamin has such a document, you can bet he's invested an
enormous amount of time and effort developing and maintaining it.
I would like to jump in here and offer some assistance (of a
different kind). Several times in my past life I needed to write an
exit of some kind. IIRC what I did was write down point by point the
information I would need to make a decision. An example would be I
needed access to a TCB or some other piece like access to the job
card or whatever. If I was writing a JES2 exit and I needed to find
some field on the job card like accounting information . I would
write that down. If I wasn't sure how to get there I would look up in
say the JES2 control blocks (it used to be in a book but I think they
stopped publishing that). I would go into browse in ISPF and do a
find for a field name that I was looking for, if that did not find it
I would use Compuware's Fileaid (there is a freebe of the CBT TAPE to
do this as well) to look through the entire PDS for the field. Once I
found it I would look to see if that field was available to me in the
exit. In other words I would have to issue another macro in order to
get addressability I would hunt that down. Usually its off the CVT
someplace or to get there I have to follow a chain off another macro.
The CVT is a great way of finding information (except JES related
stuff). The information is there (usually) (a hint here if you know
the macro name that you need to issue in the data areas in the
description of the macro it will say its pointed at by X) its just a
matter of finding what control block is needed and how to get access
to it. Sometimes its a bit perverse and it takes a few instructions
but it is (in most cases) doable. Understanding what you want and how
to get there is most of the issue. Some times it takes a few side
steps and looking into another address space and knowing how to do
that is just part of sysproging and years on the job. There are also
tidbits that you learn about getting control (properly) after reading
dumps (this is the best way to learn IMO) it comes rather easily. A
casual programmer does not see this a lot in their day to day job.
Some (INTERNAL) IBM control blocks are just not documented and if you
find one you have to figure out its layout. This is dangerous and
don't make assumptions as you will probably get an S0C4 abend or some
other abend and you are out of luck. Plus remember some control
blocks can be altered by IBM code on the fly so you have to be
careful in that as well. The TSO TEST command is nice for doing some
of the above (except cross memory) but if its in you address space
and not fetch protected then you can look to your hearts content.
Ed
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