On 8/1/2006 10:10 AM, Edward Jaffe wrote:
Paul Gilmartin wrote:
Likewise, if RET=CHNG were not available, you could equally well
simply DEQ and re-ENQ with EXCL scope.
No. Holding a shared ENQ prevents others from acquiring an exclusive ENQ
on the same resource and modifying it. To maintain the integrity of the
resource, you use RET=CHNG to upgrade from shared to exclusive without
losing control. If you were required to DEQ and then re-ENQ to perform
the upgrade, you would lose control of the resource between the time you
inspected it and the time you had the necessary serialization to update
it. In the worst case scenario, someone else could change (or even
delete) the resource in-between!!
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