Re: log file sync vs log file parallel write

Hello Steve,

I am on 9.2.0.8.
Yes the log file sync is on average 10 times the average log file parallel write .

I already came across the bug (2669566) on Jonathan Lewis is site. So probably this bug applies.

regards Hans-Peter

On 3 okt, 14:09, Steve Howard <stevedhow..._at_gmail.com> wrote:
> 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 - 07:26:03 CDT