查看执行计划的几种方法?

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我的答案

1 set autorace trace explain

2 explain plan for sql statements

select * from table(dbms_xplan.display);

3,跟踪sql的方法 alter session set sql_trace = true;

sql statements

alter session set sql_trace = off;

根据脚本查找出当前会话的spid,去 $oracle_base/admin/sid/udump/ 下去查找

跟踪其他会话 dbms_system.set_sql_trace_in_session(sid,serial#,true/false)来跟踪

4 通过用 10046调试事件来实现

level 0

level 1

level 4 bind

level 8 wait events

level 12 1+4+8

alter session set events '10046 trace name context forever,level 8

sql statement

alter session set events '10046 trace name context off';

跟踪其他会话：

sys:

exec dbms_system.set_ev(127,31923,10046,8,'A');

dbms_system.set_ev(sid,serial#,10046,8,'username');

sql statements

dbms_system.set_ev(sid,serial#,10046,0,'username');

5 :oralce 10g引入 dbms_monitors来基于客户标示符，服务名，实例，模块名 来跟踪sql

1、直接使用sqlplus系统参数：

SQL> set autotrace on explain

SQL> select * from dual;

D

-

X

Execution Plan

----------------------------------------------------------

Plan hash value: 272002086

--------------------------------------------------------------------------

| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |

--------------------------------------------------------------------------

| 0 | SELECT STATEMENT | | 1 | 2 | 2 (0) | 00:00:01 |

| 1 | TABLE ACCESS FULL | DUAL | 1 | 2 | 2 (0) | 00:00:01 |

--------------------------------------------------------------------------

SQL> set autotrace off

但是这样操作的结果是先执行SQL，再出执行计划，如果SQL耗时巨大，则不现实；

2、使用explain plan for语句：

SQL> explain plan for select * from dual;

Explained.

SQL> select * from table(DBMS_XPLAN.display);

Execution Plan

----------------------------------------------------------

Plan hash value: 2137789089

---------------------------------------------------------------------------------------------

| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |

---------------------------------------------------------------------------------------------

| 0 | SELECT STATEMENT | | 8168 | 16336 | 21 (0)| 00:00:01 |

| 1 | COLLECTION ITERATOR PICKLER FETCH| DISPLAY | | |

| |

---------------------------------------------------------------------------------------------

这样就可以在执行SQL之前查看执行计划了

3、启用SQL_TRACE跟踪所有后台进程活动：

全局参数设置：

..OracleHome/admin/SID/pfile中指定: SQL_TRACE = true (10g)

当前session中设置：

SQL> alter session set SQL_TRACE=true;

SQL> select * from dual;

SQL> alter session set SQL_TRACE=false;

对其他用户进行跟踪设置：

SQL> select sid,serial#,username from v$session where username='XXX';

SID SERIAL# USERNAME

------ ---------- ------------------

127 31923 A

128 54521 B

129 48940 B

SQL> exec dbms_system.set_SQL_TRACE_in_session(127,31923,true);

SQL> select * from dual;

SQL> exec dbms_system.set_SQL_TRACE_in_session(127,31923,false);

然后使用oracle自带的tkprof命令行工具格式化跟踪文件。

4、使用10046事件进行查询：

10046事件级别：

Lv1 - 启用标准的SQL_TRACE功能,等价于SQL_TRACE

Lv4 - Level 1 + 绑定值(bind values)

Lv8 - Level 1 + 等待事件跟踪

Lv12 - Level 1 + Level 4 + Level 8

全局设定：

..OracleHome/admin/SID/pfile中指定: EVENT="10046 trace name context forever,level 12"

当前session设定：

SQL> alter session set events '10046 trace name context forever, level 8';

SQL> select * from dual;

SQL> alter session set events '10046 trace name context off';

对其他用户进行设置：

SQL> select sid,serial#,username from v$session where username='XXX';

SID SERIAL# USERNAME

------ ---------- ------------------

127 31923 A

128 54521 B

129 48940 B

SQL> exec dbms_system.set_ev(127,31923,10046,8,'A');

SQL> select * from dual;

SQL> exec dbms_system.set_ev(127,31923,10046,0,'A');

5、使用tkprof格式化跟踪文件：

使用一下SQL找到当前session的跟踪文件：

---- 当前 session

SELECT d.value|| '/' ||lower(rtrim(i.instance, chr( 0 )))|| '_ora_' ||p.spid|| '.trc' trace_file_name

from

( select p.spid from v$mystat m,v$session s, v$process p

where m.statistic# = 1 and s.sid = m.sid and p.addr = s.paddr) p,

( select t.instance from v$thread t,v$parameter v

where v.name = 'thread' and (v.value = 0 or t.thread# = to_number(v.value))) i,

( select value from v$parameter where name = 'user_dump_dest' ) d;

---- 其他用户 session

SELECT d.value|| '/' ||lower(rtrim(i.instance, chr( 0 )))|| '_ora_' ||p.spid|| '.trc' trace_file_name

from

( select p.spid from v$session s, v$process p

where s.sid= '127' and s. SERIAL#= '31923' and p.addr = s.paddr) p,

( select t.instance from v$thread t,v$parameter v

where v.name = 'thread' and (v.value = 0 or t.thread# = to_number(v.value))) i,

( select value from v$parameter where name = 'user_dump_dest' ) d;

查找后使用tkprof命令：

SQL> $tkprof D:/....../SID_ora_5352.trc D:/....../SID_ora_5352.txt

注：无法使用autotrace的解决办法（9i）：

SQL>start $ORACLE_HOME/rdbms/admin/utlxplan.sql;

SQL>create public synonym plan_table for plan_table;

SQL>grant ALL on plan_table to public;

-The End-