Re: Oracle 10g hangs intermittently waiting for I/O

From: Paweł Kotlarz <>
Date: Fri, 15 May 2009 23:34:47 +0200
Message-ID: <>


Oracle shows many sessions waiting for direct path read (temp). Tanel's waitprof reports single events taking many seconds though most of them are below 15ms.

On the OS level vmstat shows normal reading for some time and then sessions in an uninterruptible sleep with no I/O taking place. iostat -x and asmiostat (ML 437996.1) show specific volumes. Just after the performance returns to normal these volumes show much greater queue length (iostat) or much greater average read time (asmiostat).

I ran strace on a process servicing the session on which I used waitprof earlier. It stops on a read call.

Currently I only know that the sysadmins found nothing in Linux logs and on a 'system management page'. Unfortunately it is difficult to obtain more information from them unless I tell what exactly to check...



On 2009-05-15 22:32, Rajeev Prabhakar wrote:
> Pawel,
> What things have your Storage / Linux admins looked at ? Also, from
> oracle's standpoint, what elements have you already looked at /
> already ruled out (if any) ? Please share your inputs.
> -Rajeev
> 2009/5/15 Paweł Kotlarz <>:

>> Hello all.
>> I can isolate the problem to specific disks using iostat. These disks
>> are the same on a day the problem occurs but they are different on
>> another occurrance of the problem. Storage / Linux admins do not see any
>> problem on their side.

>> Thanks.
>> Pawel Kotlarz

Received on Fri May 15 2009 - 16:34:47 CDT

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