Re: asynch descriptor resize wait event
- From: Yong Huang <yong321@xxxxxxxxx>
- To: kaygopal@xxxxxxxxx
- Date: Thu, 20 May 2010 13:28:04 -0700 (PDT)
I know what I said could be wrong, because I don't have good knowledge of this
wait event. The guess that after the event occurs, you'll see a higher value of
/proc/sys/fs/aio-max-nr cannot be right, simply because oracle, not root, has
no permission to change it.
I want to add that there doesn't seem to be a limit on a process's AIO
operations. (So the term "descriptor", usually used in the process context, is
a misleading jargon.) I thought AIO_MAX was it (as seen in "getconf -a" or
"getconf AIO_MAX", which is undefined on Linux). But man page of lio_listio(3p)
has the words "system-wide limit {AIO_MAX}".
Yong Huang
--- On Thu, 5/20/10, Yong Huang <yong321@xxxxxxxxx> wrote:
The only meaningful note on MOS I can find is 1081977.1. "This event is set
when the number of asynch descriptor reserved inside the OS kernel has to be
readjusted." On Linux, the number of system-wide AIO's is capped by
/proc/sys/fs/aio-max-nr and its current value is aio-nr. I'm guessing after the
said event occurs, /proc/sys/fs/aio-max-nr is raised. If so, and if the event
happens often, it may be a good idea to manually raise aio-max-nr (echo
some_large_number > /proc/sys/fs/aio-max-nr).
Yong Huang
-----Original message-----
This undocumented wait event is recorded when there is an underlying
IO descriptors (kiocb in linux?) needs to be adjusted. During the
time all the pending IOs are suspended momentarily and resumed after
the structure is expanded. I am not sure why this happens in an
otherwise idle database. Perhaps a bug?
On Wed, May 19, 2010 at 3:48 PM, April Sims <sims@xxxxxxx> wrote:
> Anyone know what is causing "asynch descriptor resize" wait events on
> 11gR2.(11.2.0.1)..on a test database which is mostly idle?
> Linux RH 4 - 64bit
>
> I can only find a limited amount of information on MOS and hardly anything
> in the Internet.
>
> Hanging in SQLPLUS when querying dba_autotask_client which led me to search
> for wait events.
>
> thanks
>
> April Sims
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