ORACLE查询系统中阻塞情况~

在ORACLE中经常会碰到阻塞的情况发生，这个时候我们就需要快速的找出导致阻塞的原因，并尽快排除它，好让系统重新正常运行。
下面以死锁为例，来看看如何找出导致阻塞的会话并解决问题。
//SCOTT窗口1
SQL> select * from t2;
ID
----------
3
1
2
SQL> update t2 set id=12 where id=2;
1 row updated.
SQL>
//SCOTT窗口2
SQL> select * from t2;
ID
----------
3
1
2
SQL> update t2 set id=11 where id=3;
已更新 1 行。
SQL> update t2 set id=13 where id=2;
//此时进入等待……卡住不动了
//SYS窗口
SQL> select c.terminal||' ('''||a.sid||','||c.serial#||''') is blocking '||b.sid
||','||d.serial# block_msg, a.block
2 from v$lock a,v$lock b,v$session c,v$session d
3 where a.id1=b.id1
4 and a.id2=b.id2
5 and a.block>0
6 and a.sid <>b.sid
7 and a.sid=c.sid
8 and b.sid=d.SID
9 ;
BLOCK_MSG BLOCK
---------------------------------------- ----------
HWANG ('138,305') is blocking 153,15 1
SQL> select sid,serial#,username from v$session where username is not null;
SID SERIAL# USERNAME
---------- ---------- ------------------------------
136 179 SYS
138 305 SCOTT
153 15 SCOTT
//这个时候可以杀掉那个BLOCKER
SQL> alter system kill session'138,305';
System altered.
//SCOTT窗口1
SQL> select * from t2;
select * from t2
*
ERROR at line 1:
ORA-00028: your session has been killed
SQL>