執行計劃是oracle調優的最基本方法,查看執行計劃的方法很多,下面看一下有哪些辦法直接查看執行計劃:
1、直接使用sqlplus系統參數:
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
但是這樣操作的結果是先執行SQL,再出執行計劃,如果SQL耗時巨大,則不現實;
2、使用explain plan for語句:
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 | | |
| |
---------------------------------------------------------------------------------------------
這樣就可以在執行SQL之前查看執行計劃了
3、啓用SQL_TRACE跟蹤所有後臺進程活動:
全局參數設置:
..OracleHome/admin/SID/pfile中指定: SQL_TRACE = true (10g)
當前session中設置:
SQL> alter session set SQL_TRACE=true;
SQL> select * from dual;
SQL> alter session set SQL_TRACE=false;
對其他用戶進行跟蹤設置:
SQL> select sid,serial#,username from v$session where username='XXX';
SID SERIAL# USERNAME
------ ---------- ------------------
127 31923 A
128 54521 B
129 48940 B
SQL> exec dbms_system.set_SQL_TRACE_in_session(127,31923,true);
SQL> select * from dual;
SQL> exec dbms_system.set_SQL_TRACE_in_session(127,31923,false);
然後使用oracle自帶的tkprof命令行工具格式化跟蹤文件。
4、使用10046事件進行查詢:
10046事件級別:
Lv1 - 啓用標準的SQL_TRACE功能,等價於SQL_TRACE
Lv4 - Level 1 + 綁定值(bind values)
Lv8 - Level 1 + 等待事件跟蹤
Lv12 - Level 1 + Level 4 + Level 8
全局設定:
..OracleHome/admin/SID/pfile中指定: EVENT="10046 trace name context forever,level 12"
當前session設定:
SQL> alter session set events '10046 trace name context forever, level 8';
SQL> select * from dual;
SQL> alter session set events '10046 trace name context off';
對其他用戶進行設置:
SQL> select sid,serial#,username from v$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格式化跟蹤文件:
查找後使用tkprof命令:
SQL> $tkprof D:\......\SID_ora_5352.trc D:\......\SID_ora_5352.txt