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Home -> Community -> Mailing Lists -> Oracle-L -> RE: LGWR tuning
Hi Paul,
The parameter you are looking for is probably _log_io_size (see
http://www.ixora.com.au/tips/tuning/log_buffer_size.htm), but I doubt it
can help you. One of the reasons is that IO is fragmented also at the OS
(solaris >=8 default to 1 MB if I am not wrong) and HW (storage array)
level.
Tuning to reduce the redo log volume or changing the physical device
where you write the redo logs (like avoid raid5, avoid Read/Write
contention, ..the usual stuff) is normally the way to go for this kind
of issues.
You can also recreate the redo logs in /tmp (ram disk), but that's a bit
'dangerous' and also kind of cheating.
Regards,
L.
-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Paul van den Bogaard
Sent: Tuesday, February 14, 2006 5:10 PM
To: oracle-l_at_freelists.org
Subject: LGWR tuning
During a previous benchmark I learned that the LGWR will chop writes
into chunks of max 1MB. This results in multiple AIO send to the Solaris
kernel in quick succession.
The transactions were throttled by 'log file sync' event. Another
benchmark will occurr that drives this application to even higher
limits.
I wonder/expect there is a (hidden) parameter that resets this 1MB limit
to something more appropriate.
Any clues how this parameter is called and should be set are very welcome. HInts on side effects that come for free are welcome too :-)
Thanks
Paul
Redo files are on raw devices. A single redo file is mapped on one or
more disk arrays (through host based volume management) that each have
lots of memory backed up cache. Average write time expected to be in the
sub milli second level.
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Received on Tue Feb 14 2006 - 12:01:33 CST
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