Re: Help me tuning this wait event:log file sync

From: Herman de Boer <h.de.boer_at_itcg.nl>
Date: Tue, 16 Jul 2002 08:19:01 GMT
Message-ID: <ah0kvu$e5o$1@news1.xs4all.nl>

Howard J. Rogers wrote:

>
>"Yong Huang" <yong321_at_yahoo.com> wrote in message
>news:b3cb12d6.0207151402.18ca5b57_at_posting.google.com...
>> chao_ping <chao_ping_at_163.com> wrote in message
>news:<3d312489$1_at_usenetgateway.com>...
>> > Yong Huang wrote:
>> > > If you can't control the frequency of commits, reduce log_buffer.
>How
>> > > big is it?
>> > now log buffer is 2M, In early time, it was 1M, and i see much wait time
>> > in log buffer space,(once it was the 4th top wait event), so i enlarged
>> > the log buffer size from 1m to 2m.
>>
>> Never use a log_buffer larger than 1M. It's useless over that limit.
>>
>
>Not quite true. On very heavy-transactional-load systems, a buffer uo to 5
>or 6Mb *may* (or may not!) be appropriate. Had Oracle ever decided that
>anything bigger than 1Mb was utterly "useless", they would never have
>introduced the rule about LGWR flushing every 1Mb of uncommitted redo
>(because that rule doesn't get invoked until the buffer is bigger than 3Mb,
>because of the 'flush when 1/3rd full' rule).
>

I Agree with Howard.
See also the full disclosure report of the TCP-H benchmark, 9iR2, on a HP-9000 superdome, First edition dated on 24-jun-2002.

log_buffer has been set to 32 Mbyte.

Kind Regards,

Herman de Boer
sr. consultant
IT Consultancy Group bv Received on Tue Jul 16 2002 - 03:19:01 CDT