将经常使用的表放置在db_keep_cache_size中减少物理读

以下转自：http://www.itpub.net/thread-1809208-2-1.html 作者：zcs0237

一、设置KEEP池 SYS@zcs11G>  alter system set db_keep_cache_size=32m scope=spfile; shutdown immediate; show parameter db_keep --db_keep_cache_size                   big integer 32M 二、查看数据库中已经有那些表被标记为热点表 SYS@zcs11G> select '--',owner,segment_type,segment_name,buffer_pool from dba_segments where buffer_pool != 'DEFAULT'; -- no rows selected 三、设置t11表的storage(buffer_pool keep)属性 SYS@zcs11G>  drop table t11 purge; create table t11 as select level id,lpad('z',4000,'z') name from dual  connect by level <= 5000; alter table t11 storage(buffer_pool keep); select '--',bytes/1024/1024,'MB' from dba_segments where segment_name='T11'; --              40 MB 四、查看是否在缓存keep中 SYS@zcs11G>  set pagesize 0 set autotrace off col segment_name for a12 select '--',segment_name,buffer_pool from dba_segments where buffer_pool != 'DEFAULT'; -- T11           KEEP SYS@zcs11G>  set linesize 999 select '--',a.status, count(*)  from V$BH a, user_objects b   where a.objd=b.object_id and object_name='T11' group by object_name, a.status; -- xcur             5001   T11中的数据已经全部放入KEEP池 五、体会keep池的优势 SYS@zcs11G>  set autotrace trace statistics; select count(*) from t11; Statistics ----------------------------------------------------------        140  recursive calls          0  db block gets       5090  consistent gets       5000  physical reads SYS@zcs11G>  select count(*) from t11; Statistics ----------------------------------------------------------          0  recursive calls          0  db block gets       5008  consistent gets          0  physical reads