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#1 (**permalink**) 01-05-2008, 07:03 AM

Greetings,

One of my system is p570, 4 procs, 16 GB RAM with Oracle 9iR2
installed.
AIX 5.2, ML 6
Before to use CIO on oracle FS, I configured AIO to start at boot
(minservers=20 ; maxservers per cpu=100).

Since I discovered CIO, I configured it on 2 FS (/oradata1 and
/oradata2) and changed the oracle parameter filesystemio_options from
asynch to setall

>From what I understand : if you configure setall on cio-fs, oracle uses
cio (and only in this case).

AIO consumes kernel processes.
So my questions are : is AIO still needed to be configured ? Does CIO
need AIO to be present or not ? Can I change the "STATE to be
configured at system restart" from AVAILABLE to DEFINED (smitty chaio)
?

Thank you in advance,
Wilfrid

#2 (**permalink**) 01-05-2008, 07:04 AM

Hi,
We are using Dio (Which in fact is pre requsit for Cio) for our main
Oracle DWH databases. We found ou it help improving response tiime in
20% . We use asynch in our database, Yet as I said Dio seems to work
well for us. I never heard that Cio needs
Aio. There is a very good AIX whitepaper by IBM which explains a lot
of Cio and Dio.
I shell send you the link after finding it.

#3 (**permalink**) 01-05-2008, 07:04 AM

Wilfrid Allembrand wrote:
> Greetings,
>
> One of my system is p570, 4 procs, 16 GB RAM with Oracle 9iR2
> installed.
> AIX 5.2, ML 6
> Before to use CIO on oracle FS, I configured AIO to start at boot
> (minservers=20 ; maxservers per cpu=100).
>
> Since I discovered CIO, I configured it on 2 FS (/oradata1 and
> /oradata2) and changed the oracle parameter filesystemio_options from
> asynch to setall
>
> >From what I understand : if you configure setall on cio-fs, oracle uses
> cio (and only in this case).
>
> AIO consumes kernel processes.
> So my questions are : is AIO still needed to be configured ? Does CIO
> need AIO to be present or not ? Can I change the "STATE to be
> configured at system restart" from AVAILABLE to DEFINED (smitty chaio)
> ?
>
> Thank you in advance,
> Wilfrid

yes you want to use AIO with Oracle

good database tuning guide

http://publib-b.boulder.ibm.com/redb...5511.html?Open

IBM white paper on AIO/CIO/DIO

http://www-1.ibm.com/servers/aix/whi...b_perf_aix.pdf

#4 (**permalink**) 01-05-2008, 07:04 AM

Ah ok. So if I understand well, you always need to have AIO configured
because Oracle use it for its internal mechanisms : it has nothing to
do with the options (DIO / CIO / raw) you choose to use for your fs
layout.
I am right ?

Thank you.

#5 (**permalink**) 01-05-2008, 07:04 AM

Wilfrid Allembrand wrote:
> Ah ok. So if I understand well, you always need to have AIO configured
> because Oracle use it for its internal mechanisms : it has nothing to
> do with the options (DIO / CIO / raw) you choose to use for your fs
> layout.
> I am right ?
>
> Thank you.

Yep, notice section 15.3.3 of the tuning guide relating to Oracle.

AIO is supported for all jfs type file systems, even raw devices.
Not configuring this is one of the biggest performance mistakes AIX and
Oracle DBA admins make.

If using NMON performance analyzer, the A command will show AIO stats
currently in use, peak use... etc

#6 (**permalink**) 01-05-2008, 07:04 AM

>> AIO is supported for all jfs type file systems, even raw devices.

yes, that is correct, but donot get confused by aio subsystem and
aioservers, they are 2 different things ... from the docs

"If the disk drives that are being accessed asynchronously are using a
form of raw logical volume management, then the disk I/O is not routed
through the aios kprocs. In that case the number of servers running is
not relevant."

raw lv aio is implimented in the kernel and you cannot configure it
aioservers are for jfs and jfs2 and you can configure it with your
posix_aioservers and legacy aioservers

HTH
Mark Taylor

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AIO and CIO with Oracle