At 14:14 -0400 on 05/25/2007, Bruce Black wrote about Re: Why is
there JOB scope for DSN ENQ's anyway?:
As far as a EXC-SHR function, this also seems obvious to me. The
initiator ENQs the dataset, and then releases the dataset at the end of
the last step that uses it. If you issue a EXC-SHR request, a fullowing
step may need the dataset exclusive and you have now compromised the
dataset. There is no easy way that I know to determine if the current
step is the last step that uses the dataset.
That "There is no easy way that I know to determine if the current
step is the last step that uses the dataset" claim conflicts with
your "then releases the dataset at the end of the last step that uses
it" statement.
Since it parses the job stream and sets a flag to say "You can
release the ENQ at Step Term" (as it apparently does), it can know
where the last DISP=OLD step is and do the downgrade then IF there
are one or more subsequent DISP=SHR steps (otherwise do the DEQ at
that point since this is the last step that uses the dataset).
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