Re: Async I/O

Stephane Faroult wrote:
>
> 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
> ------------------------------------------------------------------
> http://www.oriolecorp.com, designed by Oracle DBAs for Oracle DBAs
> ------------------------------------------------------------------

Steph, thanks for your reply too...

We have backup power supplys of course. Mostly we don't really care about data integrity that much. We reload a database every single night and after the load is done it's read-only. We do this from flat files etc... If the database goes mams-up we just start again although it's never happened to this day yet. It will someday I'm sure.

So not sure if this is still a problem or whether it doesn't make any diff if I turn it off or on really?

opus Received on Mon Mar 22 1999 - 15:32:40 CST