At 09:07 -0700 on 03/29/2009, Edward Jaffe wrote about Re: ENQ a
member of a PDS:
Your program should use existing ISPF serialization mechanisms. A
SPFEDIT SCOPE=SYSTEMS ENQ tells you if a data set or member is currently
being edited; a SPFEDIT SCOPE=SYSTEMS RESERVE is used to serialize
updates to the target library for data integrity. The latter might not
be necessary if the target library is a PDSE (ISPF uses it in all
cases). But, if it's a PDS, failure to properly serialize for update can
lead to unpredictable (but, predictably bad) results!
Doing the ENQ with an RNAME of DSN+MEMBER (DSN is 44 Characters right
padded and MEMBER is 8 Characters right padded for a length of 52) is
how SPF does it. There is only one GOTCHA (as there is with all the
SYSDSN type ENQs) since in a multi-CPU environment the DSN should be
unique since the VOLSER is not part of the RNAME even though SPF
KNOWS which volume the dataset is on. Thus you can be editing CPU1's
version of a data set and lock out editing of CPU2's version (on a
different volume) with the same DSN. IBM for historical reasons has
been unable to fix this design-flaw of the ENQ System since there are
components that do the ENQ before they know which volume the dataset
resides on. This should not however prevent SPF from doing ITS ENQ
with VOLSER if they wanted to fix this problem (since by the time the
ENQ is done the VOLSER is known).
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