Chris (et al.),

Thanks for the reply.  I have not replied sooner because I was hoping to get
some more feedback from the list.

I have a recently-migrated Pg cluster running 8.4.7 on Red Hat Enterprise
Linux Client release 5.7 (Tikanga) in a VMware VM that is logging the
subject warning.  The application code is considerably old (deployed back
in the 7.4 days, I believe) and the message is preceded by a call to
select user_write_unlock(), which is a simple wrapper query that calls
pg_advisory_unlock().  What are the causes and possible problems and
side-effects of receiving such a log warning?  Thank you for any
assistance you can provide.

Warning: you don't own a lock of type ExclusiveLock

That means that you didn't have the lock you were trying to release.
Whether that indicates a critical error or not depends on application
logic.

The application appears to be functioning without issue, but I still have
some concerns.  One possible cause of the warning I considered was having
the VM underlying storage NFS-mounted on a NetApp.  Is it possible that
Postgres is not receiving a meaningful response with respect to
ExclusiveLock locking (i.e. unable to really obtain an ExclusiveLock) due to
VM "disk" residing on an NFS mount?

-- Gary Chambers

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