oracle排查异常sql的一些方法

转自http://blog.itpub.net/23155850/viewspace-683737/
1、查看值得怀疑的SQL

select substr(to_char(s.pct, '99.00'), 2) || '%' load,
       s.executions executes,
       p.sql_text
  from (select address,
               disk_reads,
               executions,
               pct,
               rank() over(order by disk_reads desc) ranking
          from (select address,
                       disk_reads,
                       executions,
                       100 * ratio_to_report(disk_reads) over() pct
                  from sys.v_$sql
                 where command_type != 47)
         where disk_reads > 50 * executions) s,
       sys.v_$sqltext p
where s.ranking <= 5
   and p.address = s.address
order by 1, s.address, p.piece;

2、查看消耗内存多的sql

select b.username ,a. buffer_gets ,a.executions,
a.disk_reads/decode(a.executions,0,1,a.executions),a.sql_text SQL
from v$sqlarea a,dba_users b
where a.parsing_user_id = b.user_id 
 and a.disk_reads >10000 
order by disk_reads desc;

3、查看逻辑读多的SQL

select *
  from (select buffer_gets, sql_text
          from v$sqlarea
         where buffer_gets > 500000
         order by buffer_gets desc)
where rownum <= 30;

4、查看执行次数多的SQL

select sql_text, executions
  from (select sql_text, executions from v$sqlarea order by executions desc)
where rownum < 81;

5、查看读硬盘多的SQL

select sql_text, disk_reads
  from (select sql_text, disk_reads from v$sqlarea order by disk_reads desc)
where rownum < 21;

6、查看排序多的SQL

select sql_text, sorts
  from (select sql_text, sorts from v$sqlarea order by sorts desc)
where rownum < 21;

7、分析的次数太多，执行的次数太少，要用绑变量的方法来写sql

set pagesize 600;
set linesize 120;
select substr(sql_text, 1, 80) "sql", count(*), sum(executions) "totexecs"
  from v$sqlarea
where executions < 5
group by substr(sql_text, 1, 80)
having count(*) > 30
order by 2;

8、游标的观察

set pages 300;
select sum(a.value), b.name
  from v$sesstat a, v$statname b
where a.statistic# = b.statistic#
   and b.name = 'opened cursors current'
group by b.name;

select count(0) from v$open_cursor;

select user_name, sql_text, count(0)
  from v$open_cursor
group by user_name, sql_text
having count(0) > 30;

9、查看当前用户&username执行的SQL

select sql_text
  from v$sqltext_with_newlines
where (hash_value, address) in
       (select sql_hash_value, sql_address
          from v$session
         where username = '&username')
order by address, piece;