Re: DBWR Tuning

"Denis Do" <nospam.denisdo_at_yahoo.com> wrote in message news:slrncrq4gd.17k.nospam.denisdo_at_denisdo.news.google.com...
>>> Ref: Steve Adams - The Mysteries of DBWR Tuning
>>>
>>> We are trying to address the question "should we have multiple DBWR
>>> processes?"
>
> In Ora DB Perf Guide:
> "Multiple db writer processes are highly recommended for systems
> with multiple CPUs (at least one db writer for every 8 CPUs) or multiple
> processor
> groups (at least as many db writers as processor groups).
> Based upon the number of CPUs and the number of processor groups, Oracle
> either
> selects an appropriate default setting for DB_WRITER_PROCESSES or adjusts
> a
> user-specified setting."
>
> So, I would suggest to set at least 2 of them for start and see what
> happens.
> You definitely need more than one.

The above advice doesn't follow from the quotation. Unless you know something about the original poster that I don't. (like # of processors or processor groups he has).

> Since your OS does have async IO, you should not use IO Slaves, so both
> scans
> the buffer cache LRU and IO of those blocks
> will be performed by DBWRs - that is why you
> need more than one.

This condition will be flagged up by buffer busy waits will it not? I don't believe that every solaris system suffers from this does it?

-- 
Niall Litchfield
Oracle DBA
http://www.niall.litchfield.dial.pipex.com