Re: DB_WRITER_PROCESSES

Found that on metalink:

RDBMS Version: 8.1.7
Operating System and Version: Windows NT - 4.x Error Number (if applicable):
Product (i.e. SQL*Loader, Import, etc.): Product Version:

db_writer_processes

During setting up of multimaster asynchronous replication, it has been observed that the count value against data_blocks in v$waitstat view was increasing drastically. It had come up to a value of 70.

I observed that the db_writer_processes had a value of 1.

I tried to increase this value in the parameter file. But the value reamined as 1.

How can I tackle this error ?

From: Oracle dba 21-Jun-01 22:29
Subject: Re : db_writer_processes

You probably are running on either single CPU or two CPU NT server. By default the db_block_lru_latches parameter defaults to cpu_count/2 and that probably explains why your actual 'db_writer_processes' are always '1' even you have set it to a higher number ...

You can try to use this:
dbwr_io_slaves which is not bounded to db_block_lru_latches parameter.

Good luck.

From: Oracle, Vickie Carbonneau 22-Jun-01 19:06 Subject: Re : db_writer_processes

Hello,

Thanks for the contribution.

The data_blocks class value found in v$waitstat is a an indication that we are trying to get concurrent access to datablocks for read, insert or update purposes.

One solution is to increase the number of free lists for the affected segments.
See <Bug:733170> (which is not a bug and was opened for 7.3).

<Note:62172.1> also provides another suggestion for handling a large
number of waits on data blocks when you are seeing buffer busy waits:

Reduce number of rows per block whether changing pctfree/pctused or reducing the DB_BLOCK_SIZE.
Check for 'right-hand-indexes' (indexes that get inserted into at the same point by many processes). You can use reverse key indexes to distribute different the information.

<Note:62161.1> also provides similar suggestions.

As with DB_WRITER_PROCESSES parameter, you will need to increase the DB_BLOCK_LRU_LATCHES parameter in order for DB_WRITER_PROCESSES to be greater than 1. This is supported on Windows NT and Windows 2000.

<Note:97291.1> can assist in determining whether to use
DB_WRITER_PROCESSES or DBWR_IO_SLAVES.
Thanks,
Vickie (Oracle Support Services) Received on Fri Jan 28 2005 - 09:03:25 CST