Re: log file sync vs log file parallel write

From: Steve Howard <stevedhoward_at_gmail.com>
Date: Fri, 3 Oct 2008 05:09:14 -0700 (PDT)
Message-ID: <ec7519e0-fea6-4c98-b1e8-428d9418f2ab@l62g2000hse.googlegroups.com>


On Oct 3, 6:31 am, HansP <hans-peter.sl..._at_atosorigin.com> wrote:
> Hello all,
>
> While investigating performance problems in a database I discovered
> that the 'log file sync' wait event is almost always in the top 5.
> (I am looking at the statspack datat)
>
> Calculating the ratio of the average wait time of the 'log file sync'
> and the 'log file parallel write'  gives  a ratio of 10.
>
> Does someone know why this may happen?
>
> Regards Hans-Peter

Hi Hans-Peter,

When you say...

>>average wait time of the 'log file sync' and the 'log file parallel write' gives a ratio of 10.<<

...do you mean each log file parallel write takes ten times longer on average than each log file sync?

Also, what version are you on? There was a bug in 9i (I forget which) where "log file parallel write" was "under-reported". Jonathan Lewis had a writeup on it.

Regards,

Steve Received on Fri Oct 03 2008 - 07:09:14 CDT

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