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Home -> Community -> Usenet -> c.d.o.server -> Re: shutdown immediate or abort for cold-backup?
I would appreciate it if you could clarify this for me, I don't wish to be
argumentative, I truly want to understand.
Should the server happen to be in the midst of a large update when the instance is aborted, per the Oracle docs, processing is immediately halted and uncommitted transactions are not rolled back. It seems to me that, on restart, SMON can indeed make the instance consistent as of the last checkpoint and recover with the redo log, but it would have no way of determining how much of that update was completed prior to the abort. I think, under these circumstances, there could be a loss of data.
"Howard J. Rogers" <howardjr_at_www.com> wrote in message
news:3b8aafa0_at_news.iprimus.com.au...
> Remember that a record is kept all the time of which checkpoint sequence
> numbers are issued, and to what redo log sequence they relate. SMON
should
> therefore be very easily able to tell that all required redo for recovery
of
> an aborted mid-flight checkpoint is available in the current redo log, and
> perform automatic recovery itself without further intervention.
>
> Regards
> HJR
>
> "Charles J. Fisher" <cfisher_at_rhadmin.org> wrote in message
> news:Pine.LNX.4.33.0108271051340.9132-100000_at_galt.rhadmin.org...
> > On Sat, 25 Aug 2001, Howard J. Rogers wrote:
> >
> > > Conceivably, it would be possible to abort whilst a checkpoint is
> actually
> > > being issued, and CKPT has only got round to timestamping half the
data
> > > files... that would indeed require media recovery, but once again,
since
> all
> > > requisite redo is available in the current redo log, it wouldn't be a
> big
> > > deal.
> >
> > So, has anybody ever seen this in practice?
> >
> > I assume that, were this to occur, Oracle would complain that datafiles
> > were in need of recovery and fail to start. Hopefully, the problem could
> > be resolved by a simple "recover automatic database" since the redo
would
> > be available (sans additional archived redo).
> >
> > It seems to me, however, that this is the ONLY case where a shutdown
abort
> > would result in an (immediately) unusable database assuming that the
media
> > is intact.
> >
> > If no one has ever actually seen this in the real world, then SMON must
> > have some way of automatically "rolling back" an in-flight checkpoint.
> >
> > I myself use shutdown aborts in the cluster management software for my
> > systems, and I read earlier in this thread that Oracle-supplied HA
scripts
> > do the same. However, I would be hesitant to do a nightly shutdown abort
> > for fear of a checkpoint problem.
> >
> > It would be interesting to have a definitive answer to this question.
> > It's a shame that Oracle developers don't really seem to participate in
> > this forum.
> >
>
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