Re: Log file I/O throughput

> 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 Mon Aug 11 2003 - 06:46:45 CDT