Re: Increase in 'log file sync' waits while 'log file parallel write' remains unchanged

From: John Hurley <>
Date: Mon, 21 Sep 2009 16:34:08 -0700 (PDT)
Message-ID: <>

On Sep 21, 6:52 pm, vsevolod afanassiev
<> wrote:


> We have small database on AIX, from time to time it
> experiences waits
> on 'log file sync'. I am unable to explain these waits:
> - There is no increase in the number or size of transaction
> - While average wait on 'log file sync' increases from 10ms to 124ms
> average wait on 'log file parallel write' does not change much -
> approx 0.05 ms.

Do you have available cpu time on this system when the log file waits shoot up?

Unless you are showing some signs of severe cpu starvation ( that might have been missed possibly ) I think you gotta check out the IO subsystem.

My databases get about .5 ms for log file sync ... 10 ms is ugly and 100 ms just ouch.

Local storage or SAN? Can you get some iostat information during the bad times? Received on Mon Sep 21 2009 - 18:34:08 CDT

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