Re: Asynchronous Commit in Oracle Database 10g R2

Hi,
"Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk> wrote in message news:df9tol$oli$1_at_nwrdmz03.dmz.ncs.ea.ibs-infra.bt.com...
>
> Sorry to delay posting on this - I've been away from
> home for a while, and only been able to look at Google
> for news from time to time.
>
> This is an undocumented optimization.
> You need only look at the sessions 'redo synch writes'.
>
> This counts the calls made to the log writer to
> flush the log buffer and wait. It's always one -
> which is the one call at the end of the database
> call that contains the series of commits.
>
> The randomness of the redo writes (which
> probably matches the messages sent and
> received) is likely to be a random timing
> thing - apparently a session CAN send an
> 'unsynched' message to the log writer - and
> various things might cause this to happen.

Could you please comment on how this optimization does not create a possibility for data loss ? (An application thinks that a transaction has committed while in fact it did not, and a crash occurs ...)

Thanks.
>
>
> If you want to see the session forced to
> send a 'redo synch write' on every commit
> in the loop, then make the DML reference
> the table through a loopback link - a distributed
> transaction has to commit 'properly'.
>
>
> --
> Regards
>
> Jonathan Lewis
>
> Now waiting on the publishers: Cost Based Oracle - Volume 1
>
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>
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Received on Fri Sep 02 2005 - 16:15:38 CDT