Re: Check if async_io is enabled at disk-level

From: Deepak Sharma <>
Date: Tue, 16 Sep 2008 09:11:47 -0700 (PDT)
Message-ID: <>

It is set as follows:

SQL> show parameter filesystemio_options

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
filesystemio_options                 string      asynch

----- Original Message ----
From: "Crisler, Jon" <>
Sent: Tuesday, September 16, 2008 9:16:25 AM
Subject: RE: Check if async_io is enabled at disk-level

Check to see what the setting is for
filesystemio_options.   If = setall  this should turn on both async i/o and
direct i/o.  If this is set to none but disk_async_io = true then
I dont know what the end result would be: perhaps filesystemio_options
override disk_async_io.   Also make sure you are at a recent Maintenance Pack
for AIX as there are some known issues with Oracle (but I dont know
specifically with AIO).

________________________________ [] On Behalf Of Deepak Sharma
Sent: Tuesday, September 16, 2008
12:39 AM
Subject: Check if async_io is
enabled at disk-level

We are using ODM (Oracle Disk Manager) on one of our DBs, and the
disk_asynch_io is TRUE in the database. I have also read that ODM supports
kernel asynchronous I/O.  The platform is AIX 5.3

Using 'nmon' and choosing "A = Async I/O Servers", this is what we
see :

Total AIO processes= 100 Actually in use=   0 

This might indicate that AIO is not happening at kernel-level.  

How else can we verify if async I/O is actually happening at
Kernel-level?  We could possibly truss the DB Writer process(es) and check
for the kernel-level calls for writes - what should we look for?  Is it
kiowrite() instead of plain, write() ?


Received on Tue Sep 16 2008 - 11:11:47 CDT

Original text of this message