If defined, this function is called when shutting down the
server, following disconnection of all clients and making a
checkpoint. When a disconnect occurs as a result of server shutdown
the DBEV_DISCONNECT hook is not called and this function is
expected to perform any logout processing. The rationale is that
all disconnect hooks would be called at the same time, creating
likely deadlocks, resource contention and there could be no
guarantee of time consumed by them or of even whether they would
terminate at all.
The shutdown will do a checkpoint before calling this hook. This
checkpoint will terminate all transactions with a deadlock state.
If transactions contain automatic retries, etc..., we cannot
guarantee that all activity would have terminated when this hook
starts. However, the hook function can try
to signal an error on all other transactions to prompt them to
terminate. Again, this is not a sure-fire termination since this
could be handled by procedures.
When this hook returns the server commits the transaction in
which this was running and exits regardless of any lingering
activity. There is no hard time limit for this function. Killing
the process during this function has no specific ill effect,
besides losing uncommitted work by said function.
Result sets are prohibited, return values are discarded, errors
are logged but not otherwise processed.