Re: 'control file sequential read' high average time

From: Jonathan Lewis <>
Date: Mon, 29 Aug 2011 23:24:31 +0100
Message-ID: <>

Is any other process reading the control file ? Is any other process writing to the control file ? Does the event histogram show a normal distribution or a skew Are the rollbacks "user rollbacks" only, or "transaction rollback" as well.


Jonathan Lewis

"HansP" <> wrote in message

> Db version
> Physical standby : LGWR ASYNC
> Database on ASM.
> Application Oracle EBS
> Redo log files : 5 groups with 2 members each 500M
> Log switches: every 5 minutes
> During stress tests with about 2000 users the statistic 'user commits'
> of v$sysstat shows about 250 commits and rollbacks per second.
> The average time for 'log file sync' starts to increase until it
> reaches 490.000 usec per occurence from about 1.000 usec during off
> peak hours. The
> The average time for 'log file parallel write' increases to about
> 2.200 usec from about 700 usec during off peak hours.
> When looking in dba_hist_active_sess_history the event that occurs for
> the log writer process is 'control file sequential read' with about
> 90% of the total wait time.
> During the same time frame the average time for 'control file
> sequential read' increases to about 13.000 usec from about 45 usec
> during off peak hours.
> I am trying to figure out why there is an about 500 fold increase of
> the log file sync event.
> Could it have to do with the standby?
> Is the number of commits per second too high?
Received on Mon Aug 29 2011 - 17:24:31 CDT

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