Home » RDBMS Server » Performance Tuning » other buffer pool .... cache sizes ??
other buffer pool .... cache sizes ?? [message #191722] Thu, 07 September 2006 22:43 Go to next message
tridentadm
Messages: 142
Registered: March 2006
Senior Member
can other buffer pools have different cache sizes ??

1) keep buffer pool
and
2) recycle buffer pool

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Re: other buffer pool .... cache sizes ?? [message #191762 is a reply to message #191722] Fri, 08 September 2006 01:17 Go to previous messageGo to next message
tarundua
Messages: 1080
Registered: June 2005
Location: India
Senior Member


From Oracle Docs

Multiple Buffer Pools
You can configure the database buffer cache with separate buffer pools that either keep data in the buffer cache or make the buffers available for new data immediately after using the data blocks. Particular schema objects (tables, clusters, indexes, and partitions) can then be assigned to the appropriate buffer pool to control the way their data blocks age out of the cache.

The KEEP buffer pool retains the schema object's data blocks in memory.

The RECYCLE buffer pool eliminates data blocks from memory as soon as they are no longer needed.

The DEFAULT buffer pool contains data blocks from schema objects that are not assigned to any buffer pool, as well as schema objects that are explicitly assigned to the DEFAULT pool.

The initialization parameters that configure the KEEP and RECYCLE buffer pools are DB_KEEP_CACHE_SIZE and DB_RECYCLE_CACHE_SIZE.


Note:

Multiple buffer pools are only available for the standard block size. Non-standard block size caches have a single DEFAULT pool.

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Re: other buffer pool .... cache sizes ?? [message #191794 is a reply to message #191762] Fri, 08 September 2006 03:05 Go to previous messageGo to next message
JSI2001
Messages: 1016
Registered: March 2005
Location: Scotland
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@tarun, obviously the OP would, of course, have already read the documentation and seen this piece of information. It's just that they didn't understand it. Therefore the answer, in 1 syllable is:


No

Wink

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Re: other buffer pool .... cache sizes ?? [message #191807 is a reply to message #191794] Fri, 08 September 2006 03:52 Go to previous messageGo to next message
tarundua
Messages: 1080
Registered: June 2005
Location: India
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Here lies the problem... Not everybody look into the documentation....
Wink

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Re: other buffer pool .... cache sizes ?? [message #191809 is a reply to message #191807] Fri, 08 September 2006 03:58 Go to previous messageGo to next message
JSI2001
Messages: 1016
Registered: March 2005
Location: Scotland
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Unfortunately very true Tarun.

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Re: other buffer pool .... cache sizes ?? [message #191903 is a reply to message #191722] Fri, 08 September 2006 09:27 Go to previous messageGo to next message
goudelly
Messages: 52
Registered: August 2006
Location: India
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Hi,

keep buffer pool : The buffer cache is equal to the oracle block size.. DB_CACHE_SIZE is the default buffer cache only. It cant be zero.

DB_KEEP_CACHE_SIZE is keeps the buffer cache. Means which is keeps till you DB_KEEP_CACHE_SIZE is full.

DB_RECYCLE_CACHE_SIZE It is recycle the buffer.

For session wise you can use 'ALTER SYSTEM SET DB_CACHE_SIZE = 80M;'

You can increse the size and also decrease the size but the decrease should not be 'DB_CACHE_SIZE' size parameter.

Thses parameters you have to eable or insert in init.ora file.

Thanks,

Mohan Reddy G

Mohan Reddy G

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Re: other buffer pool .... cache sizes ?? [message #191904 is a reply to message #191903] Fri, 08 September 2006 09:32 Go to previous message
JSI2001
Messages: 1016
Registered: March 2005
Location: Scotland
Senior Member
@mOHAN,
This is the 2nd post in about as many minutes that I have seen from you where you post an answer that is only tenuously related to the question. The OP asked
Quote:

can other buffer pools have different cache sizes ??


You answer is over simplified for the points that you are trying to make e.g.


Quote:

DB_KEEP_CACHE_SIZE is keeps the buffer cache. Means which is keeps till you DB_KEEP_CACHE_SIZE is full.
Are you saying that the keep cache will be emptied once it gets full? I hope not. Do you think that mentioning the LRU algorithm might have been useful here?

The question was already CLEARLY answered by Tarun, why add to it??

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