Re: The ill effects of NOT using direct I/O

If you look in the original in the archives, it's the section where text is within quotes (").

Starts with: "With Oracle Database 10g, you can enable Direct I/O and Concurrent I/O on JFS/JFS2 at the file level."

and ends with: JFS2 file system for optimal performance."

The problem I found is the implication that dio and cio are available at file level in JFS/JFS2. jfs is *not* the same as jfs2. One of the differences is precisely that cio is not available at file level - or indeed any level - in jfs. It is available in jfs2. The text does not make that distinction clear although of course the table I indicated in the same document does so.

The other confusing bit is the "aio not available with dio". But indeed with jfs2 and cio, it is available and setting filesystemio_options = setall does nothing to stop it. In fact, it does require it - one is not able to start the db without aio enabled with smitty, if "setall" is set and jfs2 is used. I know, because it's the test I use to verify our sysadmins have configured aio properly in a new system! ;)

I've tried to make all these things a bit clearer and easy to follow in my blog post but it's not easy: there are just too many conflicting settings and OS and db options involved. That's why it is so important to declare all the conditions and pre-requisites for each choice and/or option. Bummer.

-- 
Cheers
Nuno Souto
in humid Sydney, Australia
dbvision_at_iinet.net.au



Allen, Brandon wrote,on my timestamp of 16/02/2011 9:11 AM:


> Hi Nuno, I apologize for any misinterpretation.  It is generally against the oracle-l policy to quote entire posts in replies - that's why I always try to trim them down.  My intent was only to maximize readability and comply with the list policy, not to mislead or misinterpret.  Can you please elaborate on exactly what it was you were commenting on to clear up the confusion?

>

> Cheers,



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