Re: directio and async io on redhat linux 3 and oracle 9i

From: chao_ping <zhuchao_at_gmail.com>
Date: 8 May 2005 06:33:54 -0700
Message-ID: <1115559234.033227.184010@f14g2000cwb.googlegroups.com>

Oracle metalink conflicted sometimes.
Look at note:

Doc ID: 	Note:297521.1
Subject: 	DirectIO on Redhat and SuSe Linux

Symptoms
DirectIO is used to bypass the buffer pool of the filesystem (ext2, ext3, reiserfs).

You have tried to enable the directio option by setting the init parameter
filesystemio_options=DIRECTIO

But on tracing the DBWR you dont see directio in the open system call. example
open("/tmp/test.dbf", O_RDWR|O_SYNC|O_LARGEFILE) = 21

Please remember while enabling the directio option.

• DIRECTIO is not available of the IDE disk as IDE driver does not supports varyio.
• DIRECTIO is not available on 2.4.9 Kernel. So Redhat 2.1 does not supports it.
• No extra patch is required for 10gR1

Cause

This issue has been reported in unpublished Bug 2448994

To open the database with the O_DIRECT Flag. We need to generate the 4k aligned addresss.
To achieve this we need to fix the Oracle Code to change the alignment from 512 to 4K.
Solution

The above problem can be solved by applying the Patch 2448994

After applying the patch, When we check the DBWR We can clearly see the DIRECTIO in the open system call. open("/tmp/test.dbf", O_RDWR|O_SYNC|O_DIRECT|O_LARGEFILE) = 21 References

As oracle 10g on redhat 3 support directio as Gogala said, so it means redhat 3 itself supports directio.
So the problem is how oracle use directio on redhat 3, as the note says, they don't match, so we need a seperate patch for 9.2.0.4-6 to enablee directio.

Regards
Chao Received on Sun May 08 2005 - 08:33:54 CDT