Re: WARNING:io_submit failed due to kernel limitations MAXAIO for process=128 pending aio=127
- From: Sanjeev M <sanjeevorcle@xxxxxxxxx>
- To: "Bobak, Mark" <Mark.Bobak@xxxxxxxxxxxx>
- Date: Wed, 8 Jun 2011 14:30:38 -0700
Hi Mark,
Thanks for information about on this.
We are not seeing 'async descriptor resize' wait events.
Setting on our environment for this parameter is
*cat /proc/sys/fs/aio-max-nr*
*4194304*
*grep fs.aio-max-nr /etc/sysctl.conf *
*4194304*
Nearest match that we found for this issue was in MOS support 1166003.1 has
two workarounds for similar issue:
(1) Raise the OS AIO limits such that the number of concurrent slot
requirements never exceeds the OS limit.
ie: Increase AIO-MAX-NR
OR
(2) Disable Asynchronous IO (Set DISK_ASYNC_IO=FALSE)
For 1) above We are wondering to what value this needs to be increased and
if there is any recommendation or criteria or calculation to determine the
same. May be this needs to be done using trial and error approach?
Have asked same question in oracle SR without any luck except they are
saying this is OS parameter and needs to be determined by unix admin.
Regards,
Sanjeev.
On Wed, Jun 8, 2011 at 1:49 PM, Bobak, Mark <Mark.Bobak@xxxxxxxxxxxx> wrote:
> Hi Sanjeev,
>
>
>
> Are you also seeing ‘asynch descriptor resize’ wait events?
>
>
>
> Tanel talks about this wait event, here:
>
>
> http://blog.tanelpoder.com/2010/11/23/asynch-descriptor-resize-wait-event-in-oracle/
>
>
>
> As to tuning kernel parameters, well, the error itself lists MAXAIO.
> Unfortunately, the actual tunable kernel parameter is not called ‘MAXAIO’.
> It’s ‘fs.aio-max-nr’, and can be set in /etc/sysctl.conf.
>
>
>
> What, if anything, do you have for ‘fs.aio-max-nr’ in your
> /etc/sysctl.conf?
>
>
>
> What does Oracle recommend for your 12.1.2 installation? (It may be
> different than default value for 11.1.0.7.6 database.)
>
>
>
> Looking at one of my RAC nodes, running 11.2.0.2.0, I have it set to
> 3145728.
>
>
>
> Anyhow, hope this helps you understand a bit more about aysnch I/O, the
> MAXAIO limit, and the ‘asynch descriptor resize’ wait event.
>
>
>
> -Mark
>
>
>
> PS There’s also MOS Doc ID 1081977.1, which Tanel mentions in his blog
> entry, but, there’s not much info there.
>
>
>
> *From:* oracle-l-bounce@xxxxxxxxxxxxx [mailto:
> oracle-l-bounce@xxxxxxxxxxxxx] *On Behalf Of *Sanjeev M
> *Sent:* Wednesday, June 08, 2011 4:31 PM
> *To:* ORACLE-L
> *Subject:* WARNING:io_submit failed due to kernel limitations MAXAIO for
> process=128 pending aio=127
>
>
>
> Gurus,
>
>
>
> We have recently moved from Solaris to Linux for our 12.1.2 E-business
> suite environment, RDBMS(11.1.0.7.6), GRID/ASM(11.2.0.2) and are observing
> following warnings in rdbms trace files:
>
>
>
> WARNING:io_submit failed due to kernel limitations MAXAIO for process=128
> pending aio=127
>
>
>
> Noticed that the module information in the trace files varies from job
> queue process,parallel query slave and httpd sessions.
>
>
>
> Did search for this error in MOS and got few hits but did not have an exact
> match of our situation, raised SR with oracle support.
>
>
>
> Have any of you guys encountered these warnings and know what OS parameter
> to change to fix this and any recommendation or criteria for setting value
> for maxaio.
>
>
>
> disk_asynch_io has been set to TRUE.
>
>
>
> Regards,
>
> Sanjeev.
>
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