Re: Log file I/O throughput

Thanks very much for your response.

The fact that the wait count is so high but the OS I/O is not bottlenecked must mean that the commit rate is much too high.

I will speak to the app provider about increasing the commit interval....

Matt

Stephan Bressler <agadir_at_web.de> wrote in message news:<3F378225.5000101_at_web.de>...
> > By far the most significant waits occuring in the database are for
> > 'log file sync' and 'log file parallel write'.
> ... snip
> > The reason I am hesitating is that the Unix Sys Admin (HP-UX) has run
> > some I/O diagnostics on the server (sar, glance, and iostat) and we
> > can see that there
> > is no bottleneck at the operating system level. However I know for
> > sure that Oracle is generating at least 100 x 80Mb redo log files
> > every day.
> .. snip
> > Any ideas....?
> Hi,
>
> your redo writing is fast? Still have waits?
> That usually indicates that your session are doing many short
> transactions. A session has to wait on every commit for the lgwr to
> flush the redo log buffer. Even on very fast disks this take 5-10msec,
> exspecially if you configure several log groups.
> So go and check the number of user commits and the relation of "redo
> writes" (=background writes) and "redo synch writes" (=forced writes).
> I believe the only working solution in your case to lower the commit rate.
>
> Regards
> Stephan
Received on Wed Aug 13 2003 - 06:06:36 CDT