Thanks Greg, I got your point. Well, what about my first 2 questions. How do i find that information. On Wed, Jun 3, 2009 at 12:35 AM, Greg Rahn <greg@xxxxxxxxxxxxxxxxxx> wrote: > Unless "free buffer waits" is in your top 5 wait events in > AWR/Statspack, you dont need more db writers. In almost all cases, > the default value for db_writer_processes is sufficient. > > http://download-west.oracle.com/docs/cd/B28359_01/server.111/b28274/instance_tune.htm#sthref759 > > Tuning "buffer busy waits" is different. You need to find out what > what type of buffer is being waited for and triage why. > > http://download-west.oracle.com/docs/cd/B28359_01/server.111/b28274/instance_tune.htm#sthref657 > > As a data point, the recent TPC-C that Oracle published > http://tpc.org/tpcc/results/tpcc_result_detail.asp?id=109052101 > used a db server that has 72GB RAM, multiple block caches (2k/8k/16k) > and 1 CPU (quad core Intel 5520 "Nehalem") and did over 230k tpmC > using a single db writer. > > On Tue, Jun 2, 2009 at 2:50 PM, Taral Desai <taral.desai@xxxxxxxxx> wrote: > > Reason behind this we are using 12 dbwriter process for we have 12gb of > sga > > and 10gb of pga. Some time we are getting buffer busy waits. So, need to > > find that we are using multiple buffer pools. So, if it is from there > then i > > can suggest management to use only default block size and not multiple. I > > already know that multiple buffer pool have overhead > > of managing one more memory structure so need to investigate and learn > from > > you. > > My idea is to reduce this and then start adding processes if necessary. > > > -- > Regards, > Greg Rahn > http://structureddata.org > -- Thanks & Regards, Taral Desai