Re: DBWR_IO_SLAVES and Asynchronous I/O

Sybrand Bakker <postbus_at_sybrandb.demon.nl> wrote:
>
>Asynchronous I/O is any I/O where the requestor doesn't wait for completion
>of the I/O request.
>Whether or not it is available is O/S dependent.
>Sometimes it will work on RAW devices only.
>On several systems (AIX) you need to configure it.
>If you are using asynchronous I/O you shouldn't need multiple database
>writers and/or IO slaves (that is, as far as I read the Oracle docs on this)
>If you can't use async I/O (e.g. when you don't want to use/can't use raw
>devices) in that case you need to configure I/O slaves.

You can sometimes usefully use multiple DBWRs even with async I/O, for example if DBWR is CPU bound. This can happen on large systems with many relatively slow CPUs, and a large SGA.

-- 
Andrew Mobbs - http://www.chiark.greenend.org.uk/~andrewm/