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asynchronous I/O

Paul Wasik
Frequent Advisor

asynchronous I/O

Hello, I'm trying to get a better understanding of asynchronous i/o on both Tru64 51b and HPUX 11i. I have had little success and would like any input, links to info, or general discussion.

specifically targeting the OS tasks that setup/breakdown the fuinctionality i.e. what an admin would do prior to a database/application using the asynch i/o OR undo after that DB/APP has concluded use of asynch I/o.

The history is simple, a DBA came to me indicating that the asynchronous I/O is causing issues and it needs to be 'turned off' (huh?!). I've been trying find anything to indicate the asynchtonous I/O's status or state.

thanks
5 REPLIES
Ivan Ferreira
Honored Contributor

Re: asynchronous I/O

AFAIK, from the Database perspective, Tru64 does not have anything to be "turned off" as ADVFS allows DIRECT I/O.

Oracle has this functionality compiled in it's Kernel. So, if DIRECT I/O can be enabled/disabled, is done at Oracle side.
Por que hacerlo dificil si es posible hacerlo facil? - Why do it the hard way, when you can do it the easy way?
Alexey Larin
Occasional Visitor

Re: asynchronous I/O

Ivan, do not confuse Direct I/O and Asynchronous I/O. It is different things.
About HP-UX:
VxFS does not support Asynchronous I/O. Only raw devices support Async I/O (you should configure drivers for this facility), VxFS support Direct I/O with option OlineJFS (mount options mincache=direct and convosync=direct).
About Tru64:
AdvFS support both options Direct I/O and Asynchronous I/O automatically. I think it is possible to "turn off" some of this facility on Oracle level. But it is very strange if your DBA make decision turn off Async I/O (it cans degrade performance of Data Base).
Vladimir Fabecic
Honored Contributor

Re: asynchronous I/O

See:
http://www.ixora.com.au/notes/fs_asynchronous_io.htm
I would really like to know what issues asynchronous I/O is causing.
Can you ask your DBA (since it is Oracle stuff)?
See also:
http://download-east.oracle.com/docs/html/A90347_02/appc_tru.htm
In vino veritas, in VMS cluster
Vladimir Fabecic
Honored Contributor

Re: asynchronous I/O

More about this:
http://homepage.mac.com/tikimac/papers/Oracle%20Filesystems.pdf
In vino veritas, in VMS cluster
Paul Wasik
Frequent Advisor

Re: asynchronous I/O

Well, I didn't get much informtaion on any issues or objectives for the asynchIO from the dba. I belive this was a general query to search out any potential issues. thanks for the help, I learned a little on the topic.

thanks for the help.