| db_cache_size [message #309781] |
Fri, 28 March 2008 15:07  |
lotusdeva
Messages: 201
Registered: March 2005
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Senior Member |
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Hello, we are on Oracle 10.2.3. Back in 8i (we actually used it in 9i as well) the size of the SGA was controlled by the init parameter db_block_buffers. My understanding is that this parameter is depricated since 9i, as Oracle recommends to use db_cache_size parameter. How does db_x_cache_size relate to that parameter? Does anyone know if we do not implement Automatic Shared Memory Management, what is the guideline to set db_cache_size? Our db_block_sizeis set to 8192. Also, is there a way to monitor how this setting would affect performance in 10g? Thank you!
[Updated on: Fri, 28 March 2008 15:22] Report message to a moderator |
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| Re: db_cache_size [message #309904 is a reply to message #309781] |
Sat, 29 March 2008 13:42  |
varu123
Messages: 754
Registered: October 2007
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Senior Member |
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db_cache_size parameter defines the size for the database buffer cache in the SGA.
WIth manual mode
db_cache_size= no. of buffers*db_block_size.
db_block_size represents a standard block size in your case 8k.
If you plan to use multiple block sizes in your database ,you specify db_x_cache_size parameter.
Oracle occupies separate space for these caches in SGA.
The default value is 0.
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| Re: db_cache_size [message #310202 is a reply to message #310173] |
Mon, 31 March 2008 09:57 |
lotusdeva
Messages: 201
Registered: March 2005
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Senior Member |
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Ok, got it. So DB_CACHE_SIZE should be set insead of DB_BLOCK_BUFFERS. V$DB_CACHE_ADVISE view along with V$BH and X$BH views will provide info on how many buffers to add/take away. I read the following:
Do not explicitly specify the DB_BLOCK_BUFFERS parameter in Oracle9i Database, or you will eliminate the ability of the database to dynamically reset buffer sizes.
http://www.dba-oracle.com/art_ault_optimization_parameters.htm
Are they talking about ASSM? Does ASSM automatically size db_cache_size as well?
Thank you!
[Updated on: Mon, 31 March 2008 09:58] Report message to a moderator |
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| Re: db_cache_size [message #310211 is a reply to message #310202] |
Mon, 31 March 2008 10:23 |
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Michel Cadot
Messages: 68665
Registered: March 2007
Location: Nanterre, France, http://...
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Senior Member
Account Moderator |
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I didn't read the link you posted and so can't say about this article but I warn you that many informations on this site are wrong and/or misleading.
Find your informations in Oracle doc or sites like otn or asktom, or J. Lewis site or scratchpad...
Regards
Michel
[Updated on: Mon, 31 March 2008 12:02] Report message to a moderator |
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