On Jan 6, 2008, at 1:09 PM, Lindy Mayfield wrote:
That's very helpful, Ed.
I have a file I got somewhere, don't remember, that is allocated to
ISRDDN DD and works with the ISRDDN utility. It contains lines like
this:
ASCB CVT?+C? Address Space Control Block
ASSB ASCB+150? Address Space Secondary Block
ASVT CVT+22C?+200 Address Space Vector Table (after prefix)
ASXB ASCB+6C? Address Space Extension Block
I like to use ISRDDN to make sure I'm getting the right information
and
offsets before I try to code anything. It's almost as good as
seeing it
in a dump.
Lindy
Lindy,
One thing that will help you when you start coding is to *NOT* code
hard offsets. Use the macros (data area) field names that way if the
offset should change all you should have to do is to recompile with
the correct library and it (the assembler) will figure out the
offsets for you. There might be one or two exceptions (very few) and
also use the bit names that are used in the data areas and you are
good to go. You will also get used to dsects and using statements
early on and will probably become more familiar with drop as well.
Also be careful and this is a little bit hard to write in a simple
sentence that even if you get a clean compile you should look at base
+ displacements in your code as you can sometimes pick up a "bad"
base register when you are not expecting to. Just remember to drop
the base register after you last need it. Its a little tricky at
first but once you become more proficient at the walking of registers
you will become more comfortable with this. Also this is a simple
thing to remember but *MOST* (not all) fields you are looking for are
in the first 4K of the control block. If the fields are highly used
you will probably find them in the first 100 X of the start. Again it
is not a rule just a generality (that is not always kept to). There
are some other hints but this should get you started. Just remember
USING is your friend and the data areas is the bible.
Also the more "exotic" of macro's that you use there will be more
need to recompile after each MVS maintenance cycle or SERVPAC install
as these tend to change well not often but they can and do change. If
you code your program correctly all you should need to do is
recompile. Be aware that IBM can and does change labels (rarely but
they do). Usually on obscure macros though. Again don't assume any
IBM only macro is going to contain anything at any offset. Since they
are IBM's they are pretty much free to change them at their will and
are *NOT* obligated to tell you. Good luck.
Ed
----------------------------------------------------------------------
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
