RE: log writer tuning

Oracle best practice says to put the logs in mount point separate from your data files. Obviously this is to reduce i/o conflict, since your logs will have a record of every transaction. I believe the assumption is that your redo logs will have higher i/o than any single set of data files, so putting them on their own mount point would reduce the conflict for the data. It would probably be sufficient to put your logs on a mount point with data files that are not accessed often. Perhaps you have some historic data that is rarely accessed, that could share the mount point, if that is an issue? It would also help to increase the size of your redo logs. Start by making them 4 times larger. I have used redo log sizes of up to 512m, so size isn't really a problem.

Andrew W. Kerber
Oracle DBA
UMB "If at first you dont succeed, dont take up skydiving"

-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Remigiusz Soko?owski Sent: Wednesday, February 21, 2007 8:10 AM To: Kerber, Andrew
Cc: ORACLE-L
Subject: Re: log writer tuning

Kerber, Andrew wrote:
> Definitely move the redo logs. How often are you doing log switches?
> If they database is doing them more often than every 15-30 minutes,
then
> you might want to increase the size of the redo logs.
>
> Andrew W. Kerber
> Oracle DBA
> UMB
>

Log switches are usually ~7 min. during standard work - and You are right - our needles are highest at switch time. Could anybody explain me what are technical reasons to move to separate mount point (assuming that for all file systems we use the same storage) ?
We have thought about it and in general it seems that it "depends" - separate filesystem will divide traffic on lower number of disks, so where lies profit? Is it assumption that traffic on log filesystem will be lower than on datafiles or something else?

Thanks
Remigiusz

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Remigiusz Sokolowski <rems_at_wp-sa.pl>
WP/PTI/DIP/ZAB (+04858) 52 15 770
MySQL  v.  4.x
Oracle v. 10.x
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