RE: How to set DBWR_WRITE_PROCESSES in Oracle8i?

From: Deshpande, Kirti <kirti.deshpande_at_verizon.com>
Date: Tue, 15 Jan 2002 20:25:51 -0800
Message-ID: <F001.003F0ECE.20020115200518@fatcity.com>

How long has the instance been up?

It appears that the application is trying to read the same data blocks &/or more sessions are trying to update the same data block or the free lists may need to be set properly to support concurrent INSERTs.

So, before changing anything for DBWR process, I would suggest to check the top wait events from V$SYSTEM_EVENT view. You may see high waits for 'buffer busy wait' event. If so, I would trace it further using V$SESSION_EVENT and V$SESSION_WAIT (P1, P2 values) to find out the 'hot' segment and the file. You may have to review the pctfree, freelists, extent sizes etc. to address 'buffer busy waits'.

For all you know, it could be just an application issue in scheduling the processes properly.

And to answer your question about setting DBWR_WRITE_PROCESSES(actually the parameter is DB_WRITER_PROCESSES) you may want to check out Note# 97291.1 on Metalink. It has some good information.

HTH,

Kirti

-----Original Message-----
Sent: Tuesday, January 15, 2002 7:16 PM
To: Multiple recipients of list ORACLE-L

Hi, gurus:

The database is oracle8.1.7.2.1 on win2k machine with 1 CPU and two hard drives. When I query v$waitstat, I got the following:

CLASS                   COUNT       TIME
------------------ ---------- ----------
data block          246901435  132690159
segment header           4869       8018
undo block              20986      38476
undo header              1895       1556

seems like I need to set DBWR_WRITE_PROCESSES to a higher number, what number should I choose, 2 or bigger?

Also, what other problems can you see from the last query, other than we need to add some more RBS?

Thanks,

Chris Harvest.

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Author: CC Harvest
INET: ccharvest_at_yahoo.com

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Author: Deshpande, Kirti
INET: kirti.deshpande_at_verizon.com

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