Re: 'control file sequential read' high average time
From: ddf <oratune_at_msn.com>
Date: Mon, 29 Aug 2011 13:15:39 -0700 (PDT)
Message-ID: <dab8dcb3-b93c-4157-bde8-652f8d53c386_at_d7g2000vbv.googlegroups.com>
On Aug 29, 11:09 am, Mladen Gogala <gogala.mla..._at_gmail.com> wrote:
> On Mon, 29 Aug 2011 06:18:11 -0700, HansP wrote:
> > Db version 11.2.0.2
> > 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$sysstat shows about 250 commits and rollbacks per second. The
> > average time for 'log file sync' starts to increase until it reaches
> > 490.000 usec per occurence from about 1.000 usec during off peak hours.
> > The
> > The average time for 'log file parallel write' increases to about 2.200
> > usec from about 700 usec during off peak hours. When looking in
> > dba_hist_active_sess_history the event that occurs for the log writer
> > process is 'control file sequential read' with about 90% of the total
> > wait time.
> > During the same time frame the average time for 'control file sequential
> > read' increases to about 13.000 usec from about 45 usec during off peak
> > hours.
>
> > I am trying to figure out why there is an about 500 fold increase of the
> > log file sync event.
> > Could it have to do with the standby? Is the number of commits per
> > second too high?
>
> > Any clues?
>
> > Regards HansP
>
> I have the same problem, only different application. EBS doesn't have
> much to do with this. This an ASH bug, described in the MoS document
> 941761.1. To my knowledge, this isn't fixed yet.
>
> --http://mgogala.byethost5.com- Hide quoted text -
>
> - Show quoted text -
Date: Mon, 29 Aug 2011 13:15:39 -0700 (PDT)
Message-ID: <dab8dcb3-b93c-4157-bde8-652f8d53c386_at_d7g2000vbv.googlegroups.com>
On Aug 29, 11:09 am, Mladen Gogala <gogala.mla..._at_gmail.com> wrote:
> On Mon, 29 Aug 2011 06:18:11 -0700, HansP wrote:
> > Db version 11.2.0.2
> > Physical standby : LGWR ASYNC
> > Database on ASM.
> > Application Oracle EBS
> > Redo log files : 5 groups with 2 members each 500M Log switches: every 5
> > minutes
>
> > During stress tests with about 2000 users the statistic 'user commits'
> > of v$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?
>
> > Any clues?
>
> > Regards HansP
>
> I have the same problem, only different application. EBS doesn't have
> much to do with this. This an ASH bug, described in the MoS document
> 941761.1. To my knowledge, this isn't fixed yet.
>
> --http://mgogala.byethost5.com- Hide quoted text -
>
> - Show quoted text -
Apparently there is a one-off patch for the listed bug (8682160) as listed in the above-mentioned document from MoS.
David Fitzjarrell Received on Mon Aug 29 2011 - 15:15:39 CDT