如何计算oracle的数据缓冲区命中率与共享池的命中率

--数据缓冲区命中率：
SQL> select value from v$sysstat where name ='physical reads';
SQL> select value from v$sysstat where name ='physical reads direct';
SQL> select value from v$sysstat where name ='physical reads direct (lob)';
SQL> select value from v$sysstat where name ='consistent gets';
SQL> select value from v$sysstat where name = 'db block gets';
这里命中率的计算应该是
令 x = physical reads direct + physical reads direct (lob)
命中率 =100 - ( physical reads - x) / (consistent gets + db block gets - x)*100
通常如果发现命中率低于90%,则应该调整应用可可以考虑是否增大数据缓冲区
--共享池的命中率：
SQL> select sum(pinhits-reloads)/sum(pins)*100 "hit radio" from v$librarycache;
假如共享池的命中率低于95%,就要考虑调整应用（通常是没使用bind var ）或者增加内存

 

--PGA的内存命中：

SELECT name profile,cnt,decode( total, 0, 0, round( cnt * 100 / total)) percentage
FROM ( SELECT name, value cnt, ( SUM( value ) OVER()) total
FROM v$sysstat
WHERE name LIKE 'workarea exec%');

-- 数据缓冲区高速缓存
SELECT physical_reads, db_block_gets, consistent_gets, NAME,
100 * ( 1 - ( physical_reads / (consistent_gets + db_block_gets - physical_reads))) "Data Buffer Hit Ratio"
FROM v$buffer_pool_statistics;

-- 重做日至缓冲区
SELECT a.VALUE redo_entries, b.VALUE redo_buffer_allocation_retries,
ROUND ((1 - b.VALUE / a.VALUE) * 100, 4) log_buffer_ratio
FROM v$sysstat a, v$sysstat b
WHERE a.NAME = 'redo entries' AND b.NAME = 'redo buffer allocation retries';

-- 数据字典高速缓存
SELECT SUM (pinhits) / SUM (pins) * 100 "hit radio"
FROM v$librarycache;

-- 库高速缓存
SELECT TO_CHAR (ROUND ((1 - SUM (getmisses) / SUM (gets)) * 100, 1)) || '%' "Dictionary Cache Hit Ratio"
FROM v$rowcache;

-- 排序
SELECT a.VALUE disk_sort, b.VALUE memory_sort, ROUND ((1 - a.VALUE / (a.VALUE + b.VALUE)) * 100, 4) sort_ratio
FROM v$sysstat a, v$sysstat b
WHERE a.NAME = 'sorts (disk)' AND b.NAME = 'sorts (memory)';

--找出相关的sql根据系统pid
select se.username,se.machine,sq.cpu_time,sq.sql_text from
v$process p,v$session se,v$sqlarea sq
where p.addr=se.paddr and se.sql_hash_value=sq.hash_value and p.addr='&pid';

--列出cpu_time top 10

select cpu_time,sql_text
from (select sql_text,cpu_time,
rank() over (order by cpu_time desc) exec_rank
from v$sql
)
where exec_rank <=10;

--执行次数最多的top 10
select sql_text,executions
from (select sql_text,executions,
rank() over
(order by executions desc) exec_rank
from v$sql)
where exec_rank <=10;