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Buffer Cache and Shared Pool [message #65916] Mon, 31 January 2005 11:17 Go to next message
Sarah
Messages: 15
Registered: June 1999
Junior Member
Hi All, I am new to oracle dba world. Due to bad performance, I ran statspack on my db and saw that I have a buffer cache of 380M.

Buffer Cache: 380M
Shared Pool Size: 2000M

With the Buffer Cache being that small, it is causing the disk to sort and do the majority of the work and the performance is degrading because of the server load. To increase performance, I need to do the following setting(I have required memory in my box):

Buffer Cache: 1500M
Shared Pool Size: 1000M

To increase "Buffer Cache", What parameter I should update in the init.ora file? Is it "DB_BLOCK_BUFFERS" or "DB_CACHE_SIZE".

Following is what I get in the oracle documentation:
-----------------------------------------
This parameter is deprecated in favor of the DB_CACHE_SIZE parameter. Oracle recommends that you use DB_CACHE_SIZE instead. Also, DB_BLOCK_BUFFERS cannot be combined with the new dynamic DB_CACHE_SIZE parameter; combining these parameters in the same parameter file will produce an error. DB_BLOCK_BUFFERS is retained for backward compatibility.
-----------------------------------------

Is that mean I should use only "DB_BLOCK_BUFFERS" and not "DB_CACHE_SIZE"? Or Should I use both?

Your suggestions will be much appreciated.

regards,
Sarah
Re: Buffer Cache and Shared Pool [message #65917 is a reply to message #65916] Mon, 31 January 2005 11:25 Go to previous messageGo to next message
Mahesh Rajendran
Messages: 10694
Registered: March 2002
Location: oracleDocoVille
Senior Member
Account Moderator
From oracle 9i and above use DB_CACHE_SIZE.

look into v$db_cache_advice to check whether you need to increase the allocation.

Increasing buffer cache may not always help...
Re: Buffer Cache and Shared Pool [message #65918 is a reply to message #65917] Mon, 31 January 2005 11:47 Go to previous message
Sarah
Messages: 15
Registered: June 1999
Junior Member
Thank you very much for your suggestion Mahesh,

regards,
Sarah.
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