Originally posted by: SystemAdmin

AIX 5.2 ML05
Oracle 9.2.0.8

I am trying to implement cio on an Oracle CRM database.
The data, redo and temp filesystems are mounted with the cio option. the Oracle parameter filesystemio_option is set to setall

How can I determine if cio is being used properly?

I ran a truss on an Oracle process and saw the process open a file with O_DSYNC - if cio shouldn't it use the O_CIO flag to open files?

Using lsof +fg
oracle 23187544 oracle 8u VREG R,W,DSYN,LG,0x80;CX,BR 41,1 512003 4043309197 /crmdevldata1 (/dev/crmdevldata1lv)

Shows DSYN instead of CIO.

Any help is greatly appreciated!!!

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Originally posted by: SystemAdmin

We found during our testing and implementation only those file systems containing data files (.dbf) should be mounted with the CIO option. Any other type files in those file systems will have no caching and you can take a performance hit. In addition, there is a database configuration option (filesystemI/O_option) that should be changed to setall. This lets the database know it can use the most efficient means of caching depending on filesystem mount options. These changes provided a significant increase in performance and decrease in paging space needed.
Hope this helps,
Sherry
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Originally posted by: SystemAdmin

Hi Sherry,

Thank you for your reply!

Is there a way to tell if Oracle is using cio?
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Originally posted by: SystemAdmin

This isnt' a change you can make on the fly. The file system needs to be mounted with the CIO option; you'll see it in /etc/filesystems as options = cio,rw . Before mounting the file system with the CIO option, you'll want to have the DBA make the options setting as well. A very good whitepaper on the topic can be found:
http://www-03.ibm.com/servers/enable/site/peducation/wp/9a46/9a46.pdf
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Originally posted by: SystemAdmin

Hi Sherry,

The filesystems are mounted with the cio option and the fileststemio_option is set to setall.

I would like to verify that Oracle is actually using cio (open files with O_CIO??).

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Originally posted by: SystemAdmin

Each environment we've tested, we have the DBAs run a baseline to see what performance was like before implementation. Then we umount the file systems and mount the file systems with CIO and ask them to run the identical task. That information helps us determine if performance is better or worse.

Its not something you can actually see... just symptoms of the implemented settings; performance is either better or worse. For example, paging space usage will be significantly reduced. One thing the document and other sources will tell you is that trying to use CIO with a data warehouse probably won't help and will probably adversely impact performance.
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Originally posted by: orphy

We did some tests a while back. We were able to see from both nmon and topas
that no JFS2 caching happened when CIO option was enabled.
Orphy
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