Quote from metalink: ------------------- From: Oracle, Frank Marshall 13-Nov-03 21:38 Subject: Re : dbwn VS asy io You can not use multiple DBWR's with asynch IO. You turn off asynch_io and use multiple db writers ( up to 10) or you use asynch_io and one DBWR. It is an either or situation. ---------- Also metalink note Note:97291.1 says: If the application is not very write intensive (or even a DSS system) and async I/O is available, then consider a single DBWR writer process; ------------ More, there was a bug on Solaris in the past: when both db_writer_processes and disk_asynch_io were enabled performance suffered. ---- rm On 9/9/05, Mladen Gogala <gogala@xxxxxxxxxxxxx> wrote: > > > On 09/09/2005 09:41:37 PM, Lou Fangxin wrote: > > We hit some problem on solaris with multiple db writer, and finnaly set > it > > to one, then the database run well. > > I'm running with 3 DBWR processes, for more then a year, with async I/O. > Slowaris 9, > Oracle 9.2.0.5 <http://9.2.0.5>, RAC. My users are storing documents into > the database as BLOB's and > that is very write-intensive, so I need multiple writers - 1 per I/O > controller. > No problems. The only thing that is incompatible with async I/O are I/O > slaves, which > are intended to simulate async I/O. That is explained in the note 97291.1. > However, on HP-UX it is not recommended to use multiple DBWR processes and > async I/O. > This is an old information, from the time that I was working for OXHP, > which used to > have 4-way OPS (not RAC) system. I remember oracle support guy telling me > that it is > not advised to use that combo on HP-UX 11.0. It was a brand new system, we > finished > transition from an old Siemens Reliant Unix to HP-UX on Sunday, > 09/09/2001. Tomorrow, > on Monday 09/10/2001 I was very busy solving various problems, but > everything was successful > in the end. I thought that I will relax a bit as of the day after. The day > after was, of > course, Tuesday 9/11/2001 and the world as I knew it ended that day. > > -- > Mladen Gogala > http://www.mgogala.com > > >