Friday, October 26, 2012

0 Large Pool

Large Pool’s purpose is similar to Shared Pool. The major difference is it would be only used in the certain circumstances.

  • In MTS( Multi-threaded server) env, use for soft area and hash area.
  • Parallel Query
  • Large file’s IO Buffer
  • RMAN’s IO Buffer

Description of Figure 14-1 follows

* Image is from Oracle

Default value for Large Pool is 0. Max size is 2GB ( vary by os).

Unlike shared pool, Large Pool does not use LRU. Memory only can be free up when it is done using.

In MTS environment, if it large Pool is set. use large pool for UGA, otherwise, UGA is in the shared pool.

 

How to check the large pool size?

show parameter large_pool
select * from v$sgainfo;
select * from v$sgastat where pool='large pool';

 

image

_LARGE_POOL_MIN_ALLOC

Allocation size for the large pool.

col Parameter format a30
col value format a30
select a.ksppinm "Parameter", b.ksppstvl "Value" from x$ksppi a, x$ksppcv b 
where a.indx = b.indx and a.ksppinm like ('%large_pool_min_alloc%');

image

How to change the large Pool size?

alter system set large_pool_size=XXX; 

image

parallel_automatic_tuning

parallel_automatic_tuning is to enable the parallel execution.

image

 

Reference

http://docs.oracle.com/cd/E14072_01/server.112/e10820/initparams105.htm

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