Re: Async I/O

Hello Stephane,

I don't think that your statement is true. =

Oracle will be clever enough to open the redo log files with the O_SYNC flag. =

Stephane Faroult wrote:
> =

> 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, whe=
n
> 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 hardwar=
e
> behaves (i.e. if it has some battery to cope with a power failure). Thi=
s
> is why async I/O may indeed work well with anything, until ..., but als=
o
> 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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> http://www.oriolecorp.com, designed by Oracle DBAs for Oracle DBAs
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Received on Tue Mar 23 1999 - 01:35:32 CST