oracle 中如何定位重要(消耗资源多)的SQL_oracle定位io过高的语句-优快云博客

本文提供了一系列针对Oracle数据库的SQL性能分析方法，包括如何查找高负载、高内存使用、高逻辑读取、高执行频率等SQL语句。通过这些实用的查询语句，可以帮助数据库管理员快速定位性能瓶颈。

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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

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;



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