Re: log_file_sync io wait question

What about Steve Adam's comments at:

http://www.ixora.com.au/tips/tuning/log_buffer_size.htm

What results have been achived by tweeking _log_io_size settings? I was about to poke around with this.

"Of course, it is not necessary to carefully balance log buffer space waits against log file sync waits. You can have both a large log_buffer setting to avoid log buffer space waits, and a relatively small _log_io_size setting to minimize log file sync waits and reduce their duration."

On Wed, Sep 18, 2002 at 09:08:32AM -0800, Pat Howe wrote:
> We have a canned package that we use to insert approx 100 records/second
> into one table (oltp environment).
> Each record is just under 1K (datatypes = number and varchar).
> There are several indexes that are build on the table as the records are
> inserted.
> Each and every record is committed.
> Therefore we are flushing the 'redo log buffer' to disk (online redo
> logfiles) 100 times per second (once per commit).
>
> Not surprisingly we have noticed IO waits which we believe are associated
> with our 'Redo Log buffer'. Namely ;
> log_file_sync = 180 waits/sec
> log_file_parallel_write = 180 waits/sec
>
> We tried resizing the 'redo log buffer' from 16K to 256K - but we did not
> notice any improvements.
> Neither Log switching or archiving seem to be excessive.
> 100 records per second seems to be our maximum speed without the application
> queuing up and Oracle showing very high waits on log_file_sync and
> log_file_parallel_writes.
>
> Does anyone know how we might be able to minimize the IO waits?
>
> Thanks in advance.
>
> ENVIRONMENT
> oracle : Oracle 8.1.7.4
> os : Sun Sparc Solaris 8
> box : 8x8 E10K
> IO : Hitachi SANS unit through fiber and Brocade switch
>
>
> _________________________
> Patrick J. Howe
>
>
>
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> Author: Pat Howe
> INET: PHowe_at_verisign.com
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-- 
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Ray Stell   stellr_at_vt.edu     (540) 231-4109     KE4TJC    28^D
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