在分析SQL性能的時候，經(jīng)常需要確定資源消耗多的SQL，總結(jié)如下： 1 查看值得懷疑的SQLselect substr(to_char(s.pct,

在分析SQL性能的時候，經(jīng)常需要確定資源消耗多的SQL，，總結(jié)如下：

1 查看值得懷疑的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 查看消耗內(nèi)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 查看邏輯讀多的SQL

select*

from(select buffer_gets, sql_text

from v$sqlarea

where buffer_gets>500000

order by buffer_gets desc)

where rownum<=30;

4 查看執(zhí)行次數(shù)多的SQL

select sql_text, executions

from(select sql_text, executions from v$sqlarea order by executions desc)

where rownum<81;

5 查看讀硬盤多的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 分析的次數(shù)太多，執(zhí)行的次數(shù)太少，要用綁變量的方法來寫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 游標(biāo)的觀察

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 查看當(dāng)前用戶&username執(zhí)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;

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