ORACLE 查看CPU使用率最高的语句及一些性能查询语句

  select * from (select sql_text,sql_id,cpu_time from v$sql order by cpu_time desc) where rownum<=10 order by       rownum asc ;

select * from (select sql_text,sql_id,cpu_time from v$sqlarea order by cpu_time desc) where rownum<=10 order by rownum asc ;

这2个语句效果基本一样，一个从v$sql视图查询一个从v$sqlarea视图查询。

列出使用频率最高的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 <=5;

消耗磁盘读取最多的sql top5：
select  disk_reads,sql_text
from  ( select  sql_text,disk_reads,
   dense_rank() over
     ( order  by  disk_reads  desc ) disk_reads_rank
   from  v$sql)
where  disk_reads_rank <=5;

找出需要大量缓冲读取（逻辑读）操作的查询：
select  buffer_gets,sql_text
from  ( select  sql_text,buffer_gets,
   dense_rank() over
     ( order  by  buffer_gets  desc ) buffer_gets_rank
   from  v$sql)
where  buffer_gets_rank<=5;