Re: DB_WRITER_PROCESSES vs DBWR_IO_SLAVES

There could be some interaction.

If DBWR needs to write a block for
which the most recent changes are in
the log buffer but not in the log file, then DBWR posts LGWR to write - and in
earlier versions of Oracle DBWR would
then wait for LGWR to sync, in later versions DBWR links the buffer to a holding list
carries on down it's main write list and comes back later to pick up the spares
(I think).

It is possible that this type of cross-over could produce some redo latch pressure
in the right circumstances.

Regards

Jonathan Lewis
http://www.jlcomp.demon.co.uk

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• Original Message ----- To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Saturday, January 10, 2004 8:29 AM

> Since when is redo log writing
> performance handled by DB_WRITERS
> or DBWR_IO_SLAVES?
>
> Cheers
> Nuno Souto
> nsouto_at_optusnet.com.au
> ----- Original Message -----
>
>
> Now, the Sr DBA here is screaming about the performance since I made the
> change,
> in particular, he says he's seeing high redo latch contention and redo
> log
> buffer waits which he says validates his contention that we need to get
> back to
> using DBWR_IO_SLAVES.
>

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Author: Jonathan Lewis
  INET: jonathan_at_jlcomp.demon.co.uk

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