Log file I/O throughput

I'm looking for some clarification about a log file I/O bottleneck I have identified on one of my databases.

By far the most significant waits occuring in the database are for 'log file sync' and 'log file parallel write'.

These wait events normally go hand in hand because while the LGWR process is waiting for a write to the online log file to complete
(i.e. log file par write), the users often wait for 'log file sync'.

Since these 2 waits account for over half of total service time, I have come to the conclusion that I have a log file I/O bottleneck. The sensible thing to do to solve this would be to relocate the mirrored copies of my redo log files onto a dedicated disk
(unfortunately both members are currently in the same filesystem). Or
to drop the mirrored copy altogether since redundancy in built into the I/O subsystem (Hitachi S.A.N).

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.

So I cant co-relate the statistics in Oracle's v$ tables with the feedback from the OS performance utilities.

Any ideas....?

Matt Received on Fri Aug 08 2003 - 06:03:55 CDT