McKown, John wrote:
I'm curious if anybody knows how z/OS actually processes the OPEN for a
DUMMY DD statement. I know that basically output is ignored and input
causes an immediate EOF. But I wondering if OPEN is smart enough that if
a file is opened for OUTPUT, the address in the DCB is simply to a
IEFBR14 type module, or is it more complicated that that? Does it even
bother to validate the LRECL, BLKSIZE, and RECFM? If so, why? Just to be
compatible? Does it bother to get I/O buffers? Why?
I guess INPUT would be more difficult, but perhaps a dynamically created
I/O module which invokes the EODAD immediately or goes to an ABEND
subroutine if there is no EODAD or if the EODAD is to be executed a
second time. Same question about LRECL, BLKSIZE, RECFM, and I/O buffers.
Just curious at the end of the year freeze.
OPEN gets invoked, and you can tell because you
need to ensure you have DCB parameter stuff or
you get an 013-xx error; but it's hard to tell if
an access method module is located or if buffers
are actually obtained.
Kind regards,
-Steve Comstock
The Trainer's Friend, Inc.
303-393-8716
http://www.trainersfriend.com
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