RE: Log File Sync to Log File Parallel Write Ratio

From: Christopher Spence <cspence_at_FuelSpot.com>
Date: Fri, 15 Jun 2001 17:29:45 -0700
Message-ID: <F001.0032C1F2.20010615164023@fatcity.com>

log file sync includes the time it takes to post the LGWR process as well as the time it takes to flush the buffer down to the datafile.

log file parallel write is only the time it takes to write out the log information to disk.

So in short, log file parallel waits shows delay in IO to actually process the write. Where as significantly higher log file sync wait time over the log file parallel waits shows contention on the LGWR and it's latches.

Steve, please correct me if I am wrong with this assesment.

This is something my research has always lended me to believe.

"Walking on water and developing software from a specification are easy if both are frozen."

Christopher R. Spence
Oracle DBA
Fuelspot

-----Original Message-----

Sent: Thursday, June 14, 2001 9:46 PM
To: Multiple recipients of list ORACLE-L

Looking at some old Q&A on Steve's site (www.ixora.com.au) and found a post containing this...

"The ratio of your log file sync to log file parallel write waits indicates that your log_buffer is much too big. Drop it back to 160K. "

What exactly is the ratio suppose to be and how do these two wait events differ exactly.

Thanks,
Ethan Post

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Author: Post, Ethan
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Author: Christopher Spence
INET: cspence_at_FuelSpot.com

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