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Home -> Community -> Usenet -> c.d.o.server -> Re: Async I/O
opus wrote:
>
> Hello all,
>
> Now someone else from Oracle support sends me FAQ
> saying I shouldn't use asyn I/O with JFS but there's no reason as to
> what can happen if you do. So far been running like this for quite
> awhile. Any thoughts?
>
> Opus
The problem of async I/O is a data integrity problem. The purpose of a
RDBMS is to ensure that any committed transaction has indeed being
written to disk - this is the purpose of the log writer. Basically, when
you say 'commit', then the log writer writes the log buffer to the redo
log file, and when it is safely written on disk you get a 'committed'
acknowledgement. If you use async I/O it just means that you send a
write command, and anticipate a successful return. The question is then
what will happen if somebody unplugs your computer at this crucial
moment? It depends on how your buffers are managed and how your hardware
behaves (i.e. if it has some battery to cope with a power failure). This
is why async I/O may indeed work well with anything, until ..., but also
why Oracle support people will only recommend it when it's totally safe.
Who do you think you are going to blame if you ever have a data
integrity problem ?
--
Regards,
Stéphane Faroult
Oriole Corporation
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