Re: excessive number of db writer

  • From: amonte <ax.mount@xxxxxxxxx>
  • To: "K Gopalakrishnan" <kaygopal@xxxxxxxxx>
  • Date: Wed, 6 Sep 2006 11:42:07 +0200


This is a OLTP CRM system which supports 4000 concurrent users, concurrent
active users probably around 70, 80.

I just been told its not from an Oracle Consultant, it is from a TEAM of
them! 2 from Oracle On Site Support DBA, 2 from some other Consultancy.

The reason of changing row cache, shared subpool and shared pool latches is
because they say they migrated some billing system last year from 8i to 9i
and the systme run smoothly with these settings.

Regarding DBWR, this one got me, the reasong they give to me is just to
increase the number of CACHE LRU LATCHES! I thought you could increase that
using _db_block_lru_latches instead of messing around database writers....

Well you know, I can discuss with one but against 4 and two are from Oracle



On 9/6/06, K Gopalakrishnan <kaygopal@xxxxxxxxx> wrote:


Did you get  an explanation for those suggestions?  It would be difficult
for us to comment on those changes without any additional details..

However, However,However, 20 DBWriters are certainly high for your
configuration ;)

Have a nice day !!
Best Regards,
K Gopalakrishnan,
Co-Author: Oracle Wait Interface: Oracle Press 2004.

Coming Soon: Oracle RAC Handbook, Oracle Press 2006

----- Original Message ---- From: amonte <ax.mount@xxxxxxxxx> To: oracle-l@xxxxxxxxxxxxx Sent: Wednesday, September 6, 2006 1:39:51 AM Subject: excessive number of db writer


I have been suggested by some Oracle Consultant to set 20 Database Writer
in a 12 CPU HP-UX Server.

Does anyone know what are the side effects of having excessive DBWR? I
detected a higher CPU usage (between, 1% to 2%) not sure if its due to the
number of Database Writer. Because when I increased the number of DBWR at
init.ora I also changed these parameters

_row_cache_cursors = 60
_kgl_latch_count = 59
_kghdsidx_count = 4
statistics_level = basic

again suugested by this guy.



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