db_cache命中率

Data Buffer里各个区域里的命中率查询
SELECT name,1-(physical_reads / (db_block_gets +consistent_gets)) "HIT_RATIO"
FROM sys.v$buffer_pool_statistics
WHERE  db_block_gets + consistent_gets > 0;

示例1：
SQL> SELECT name,1-(physical_reads / (db_block_gets +consistent_gets)) "HIT_RATIO"
  2  FROM sys.v$buffer_pool_statistics
  3  WHERE  db_block_gets + consistent_gets > 0;

NAME                  HIT_RATIO
-------------------- ----------
DEFAULT              .996046807

 

示例2：
SQL> SELECT name,1-(physical_reads / (db_block_gets + consistent_gets)) "HIT_RATIO"
 2   FROM   sys.v$buffer_pool_statistics
 3   WHERE  db_block_gets + consistent_gets > 0;

NAME                HIT_RATIO
------------------ ----------
KEEP               .983520845
RECYCLE            .503866235
DEFAULT            .790350047