查看性能差的sql语句
查询出性能最差的10条sqlSELECT * FROM (select PARSING_USER_ID,EXECUTIONS,SORTS,
COMMAND_TYPE,DISK_READS,sql_text FROM v$sqlarea
order BY disk_reads DESC )where ROWNUM 10000000 OR disk_reads > 1000000
ORDER BY buffer_gets + 100 * disk_reads DESC;
DISK_READS：表示物理读的数量。
分析性能差的sql
SELECT EXECUTIONS , DISK_READS, BUFFER_GETS,
ROUND((BUFFER_GETS-DISK_READS)/BUFFER_GETS,2) Hit_radio,
ROUND(DISK_READS/EXECUTIONS,2) Reads_per_run,
SQL_TEXT
FROM V$SQLAREA
WHERE EXECUTIONS>0
AND BUFFER_GETS >0
AND (BUFFER_GETS-DISK_READS)/BUFFER_GETS < 0.8
查询共享池中已经解析过的SQL语句及其相关信息
--EXECUTIONS 所有子游标的执行这条语句次数
--DISK_READS 所有子游标运行这条语句导致的读磁盘次数
--BUFFER_GETS 所有子游标运行这条语句导致的读内存次数
--Hit_radio 命中率
--Reads_per_run 每次执行读写磁盘数
笼统的说EXECUTIONS，BUFFER_GETS，Hit_radio越高表示读内存多，磁盘少是比较理想的状态，因此越高越好
另外两个越高读磁盘次数越多，因此低点好
获取执行次数最多的10个SQL
select sql_text,executions
from (
select sql_text,executions,rank() over(order by executions desc) exec_rank
from v$sql
)
where exec_rank 1
)
)
where exec_rank100000
or disk_reads > 100000
order by buffer_gets+100*disk_reads desc
前5个花费最多CPU和时间：
select sql_text,executions,
round(elapsed_time/1000000,2) elapsed_seconds,
round(cpu_time/1000000,2) cpu_secs from
(select * from v$sql order by elapsed_time desc)
where rownum100 or m.CPU>100 or m.LOGICAL_READS>100) and m.session_id=s.SID and m.SESSION_SERIAL_NUM=s.SERIAL# order by m.PHYSICAL_READS DESC,m.CPU desc,m.LOGICAL_READS desc;
查询使用频率最高的5个查询：
select sql_text,executions from (select sql_text,executions, rank() over (order by executions desc) exec_rank from v$sql) where exec_rank
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