-----Original Message-----
From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On
Behalf Of Kenneth J. Kripke
Sent: Sunday, July 18, 2010 5:09 PM
To: IBM-MAIN@bama.ua.edu
Subject: Detecting when a READ/GET crosses a concatenation boundary
Hello;
I wish to detect when a BSAM read or QSAM GET crosses a
concatenation boundary.
I am guessing I need to code an OPEN and EOV DCB exit to get control.
The input data sets can reside on DASD or TAPE, but,
the environment does not mix unlike devices...all one way or the other.
Purpose:
Be able to the extract the dsn actively being processed. Environment
has specifc dsn naming conventions that tie back to a cycle number and
the generating jobstream.
Any assistance/tips would be greatly appreciated.
<SNIP>
"DFSMS Using Data Sets" gives some tips in this area. Look at the area
covering "Concatenating Data Sets Sequentially".
The OPEN exit is driven for each data set in the concat as the Access
Method switches to it. So from this, you should be able to get the DSN.
And the Label exits get driven as well.
Take a look at "Using Non-VSAM User-Written Exit Routines" with the
specifics of "Open/Close/EOV Standard User Label Exit".
So you are on the right track. Beware of mixed mode (24/31 bit
addressing), it can get you really lost when trying to diagnose a
problem.
Also, look out for LBI -- you have said something about tapes. They can
be in LARGE BLOCK (>32K) and certain things may be different for the
exits (I can't remember exactly how that works -- I get to diagnose
problems with our code from time to time).
Regards,
Steve Thompson
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