-----------------------<snip>-----------------------
I'm trying to write some code that performs random access I/O on a
multi volume dataset using a technique similar to that described in
chapter 7 of DFSMSdfp Advanced Services, and am having mixed results.
The code all works just fine, so long as the dataset I'm dealing with
exists already, or is allocated in a previous step of my job using,
for example, an EXEC PGM=IEFBR14 step. If I try and allocate the
dataset in the step that actually performs the I/O as a
DISP=(NEW,CATLG) or DISP=(NEW,DELTE) dataset, then when I try and open
specific volumes by changing the JFCBVLSQ field in the JFCB prior to
performing an OPEN TYPE=J, then I don't get the right volume. It seems
to me like I always get the first volume. I don't believe that there's
anything fundamentally wrong with the code as it works fine if I
allocate an empty multivolume dataset and reference it as DISP=OLD in
the step that's going to do the work. I also get similar problems if I
use DISP=MOD, only this time I get only either the first or the last
volume -- try and open anything in the middle and I always get the
last. This I wasn't so worried about since I get just use DISP=OLD
instead and this works fine.
So I guess my question is, is OPEN TYPE=J specifying the JFCBVLSQ
field supposed to work on DISP=NEW datasets? Has anyone had success
with this?
Current this is a bit of a show stopper for us as ideally we need to
be able to use a multivolume temporary dataset (so declared
DISp=(NEW,DELETE,DELETE) with a DSN of something like &&WPSTEMP).
-----------------------------<unsnip>-----------------------
Dumb question: While you're doing this random access, is there any data
at the points you're trying to access? Most, though perhaps not all,
random access dataset have data pre-loaded, or at least the areas being
accesses are pre-formatted. We need more information about what you're
trying to accomplish before we can even postulate a theory about your
problem. Why multi-volume? Why temporary? How is it being used?
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