下面查询可以查到死锁，但是注意其实查询到的不是真正的死锁，查询到的只是是死锁发生前的等待条件，真正的死锁在10G中会被系统所阻止掉
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select t2.username||' '||t2.sid||' '||t2.serial#||' '||t2.logon_time||' '||t3.sql_text
from v$locked_object t1,v$session t2,v$sqltext t3
where t1.session_id=t2.sid
and t2.sql_address=t3.address
order by t2.logon_time ;
此外，从V$LOCK的BLOCK字段可以看到，BLOCK0表示有等待发生了，注意是行级等待，而在表级没有死锁或等待
select * from v$lock where block0 ;
1.可能在Oracle中可以有计时器,在频繁操作数据库,update,insert,delete语句,在jobs中能查看到（如图）
2.可能在.net程序中使用到timer控件,频繁的操作数据库update,insert,delete语句（如图）
3.可能在.net程序中使用到Thead(线程）频繁的操作数据库update,insert,delete语句（这个条为个人观点，还未得到证实）
【注释】：此处更新数据量都比较大,比如说update的数据库条数可能在1000条以上，
导致其他操作在等待（update跟其他操作都是同一张表）
4.可能使用到事务处理（Tran）,没有提交事务（CommintTran）或者没有回滚事务(Rollback)
【注释】:在SqlServer数据库里面有一个隐式事务,关闭时候,每次修改插入都需要手动提交,不然就会导致死锁
-- 死锁查询语句
SELECT bs.username "Blocking User", bs.username "DB User",
ws.username "Waiting User", bs.SID "SID", ws.SID "WSID",
bs.serial# "Serial#", bs.sql_address "address",
bs.sql_hash_value "Sql hash", bs.program "Blocking App",
ws.program "Waiting App", bs.machine "Blocking Machine",
ws.machine "Waiting Machine", bs.osuser "Blocking OS User",
ws.osuser "Waiting OS User", bs.serial# "Serial#",
ws.serial# "WSerial#",
DECODE (wk.TYPE,
'MR', 'Media Recovery',
'RT', 'Redo Thread',
'UN', 'USER Name',
'TX', 'Transaction',
'TM', 'DML',
'UL', 'PL/SQL USER LOCK',
'DX', 'Distributed Xaction',
'CF', 'Control FILE',
'IS', 'Instance State',
'FS', 'FILE SET',
'IR', 'Instance Recovery',
'ST', 'Disk SPACE Transaction',
'TS', 'Temp Segment',
'IV', 'Library Cache Invalidation',
'LS', 'LOG START OR Switch',
'RW', 'ROW Wait',
'SQ', 'Sequence Number',
'TE', 'Extend TABLE',
'TT', 'Temp TABLE',
wk.TYPE
) lock_type,
DECODE (hk.lmode,
0, 'None',
1, 'NULL',
2, 'ROW-S (SS)',
3, 'ROW-X (SX)',
4, 'SHARE',
5, 'S/ROW-X (SSX)',
6, 'EXCLUSIVE',
TO_CHAR (hk.lmode)
) mode_held,
DECODE (wk.request,
0, 'None',
1, 'NULL',
2, 'ROW-S (SS)',
3, 'ROW-X (SX)',
4, 'SHARE',
5, 'S/ROW-X (SSX)',
6, 'EXCLUSIVE',
TO_CHAR (wk.request)
) mode_requested,
TO_CHAR (hk.id1) lock_id1, TO_CHAR (hk.id2) lock_id2,
DECODE
(hk.BLOCK,
0, 'NOT Blocking', /**//* Not blocking any other processes */
1, 'Blocking', /**//* This lock blocks other processes */
2, 'Global', /**//* This lock is global, so we can't tell */
TO_CHAR (hk.BLOCK)
) blocking_others
FROM v$lock hk, v$session bs, v$lock wk, v$session ws
WHERE hk.BLOCK = 1
AND hk.lmode != 0
AND hk.lmode != 1
AND wk.request != 0
AND wk.TYPE(+) = hk.TYPE
AND wk.id1(+) = hk.id1
AND wk.id2(+) = hk.id2
AND hk.SID = bs.SID(+)
AND wk.SID = ws.SID(+)
AND (bs.username IS NOT NULL)
AND (bs.username 'SYSTEM')
AND (bs.username 'SYS')
ORDER BY 1;
查询发生死锁的select语句
select sql_text from v$sql where hash_value in (
select sql_hash_value from v$session where sid in (select session_id from v$locked_object)
)
Oracle数据库出现死锁的时候可以按照以下处理步骤加以解决：
第一步：尝试在sqlplus中通过sql命令进行删除，如果能够删除成功，则万事大吉！但通常情况下，出现死锁时，想通过命令行或者通过Oracle的管理工具删除有死锁的session，oracle只会将该session标记为killed，但无法清除掉，往往需要通过第二步在操作系统层级进行删除！
Connected to Oracle9i Enterprise Edition Release 9.2.0.1.0
Connected as quik
SQL select xidusn, object_id, session_id, locked_mode from v$locked_object; --查死锁的对象，获取其SESSION_ID
XIDUSN OBJECT_ID SESSION_ID LOCKED_MODE
---------- ---------- ---------- -----------
10 30724 29 3
10 30649 29 3
SQL select username,sid,serial# from v$session where sid=29; --根据上步获取到的sid查看其serial#号
USERNAME SID SERIAL#
------------------------------ ---------- ----------
QUIK 29 57107
SQL alter system kill session '29,57107'; --删除进程，如已经删除过，则会报ora-00031的错误；否则oracle会将该session标记为killed状态，等待一段时间看能否会自动消失，如长时间消失不掉，则需要做后续步骤
alter system kill session '29,57107'
ORA-00031: session marked for kill
SQL select pro.spid from v$session ses,v$process pro where ses.sid=29 and ses.paddr=pro.addr; --查看spid号，以便在操作系统中根据该进程号删除进程
SPID
------------
2273286
第二步：进入操作系统进行删除进程，本示例的操作系统是IBM aix。
login: root --录入用户名
root's Password: --录入密码
*******************************************************************************
* *
* *
* Welcome to AIX Version 5.3! *
* *
* *
* Please see the README file in /usr/lpp/bos for information pertinent to *
* this release of the AIX Operating System. *
* *
* *
*******************************************************************************
Last unsuccessful login: Fri Apr 23 14:42:57 BEIDT 2010 on /dev/pts/1 from 10.73
.52.254
Last login: Fri Apr 23 15:27:50 BEIDT 2010 on /dev/pts/2 from 10.73.52.254
# ps -ef|grep 2273286 --查看进程详情
root 2289864 2494636 0 17:07:15 pts/1 0:00 grep 2273286
oracle 2273286 1 0 14:38:24 - 0:21 oracleQUIK (LOCAL=NO)
# kill -9 2273286 --删除进程，小心操作，别写错进程号，如果oracle的关键进程被删，数据库会崩溃的！
# ps -ef|grep 2273286 --再次查看
root 2289864 2494636 0 17:07:15 pts/1 0:00 grep 2273286
For Windows, at the DOS Prompt: orakill sid spid
For UNIX at the command line kill –9 spid
-- 死锁查询语句
SELECT bs.username "Blocking User", bs.username "DB User",
ws.username "Waiting User", bs.SID "SID", ws.SID "WSID",
bs.serial# "Serial#", bs.sql_address "address",
bs.sql_hash_value "Sql hash", bs.program "Blocking App",
ws.program "Waiting App", bs.machine "Blocking Machine",
ws.machine "Waiting Machine", bs.osuser "Blocking OS User",
ws.osuser "Waiting OS User", bs.serial# "Serial#",
ws.serial# "WSerial#",
DECODE (wk.TYPE,
'MR', 'Media Recovery',
'RT', 'Redo Thread',
'UN', 'USER Name',
'TX', 'Transaction',
'TM', 'DML',
'UL', 'PL/SQL USER LOCK',
'DX', 'Distributed Xaction',
'CF', 'Control FILE',
'IS', 'Instance State',
'FS', 'FILE SET',
'IR', 'Instance Recovery',
'ST', 'Disk SPACE Transaction',
'TS', 'Temp Segment',
'IV', 'Library Cache Invalidation',
'LS', 'LOG START OR Switch',
'RW', 'ROW Wait',
'SQ', 'Sequence Number',
'TE', 'Extend TABLE',
'TT', 'Temp TABLE',
wk.TYPE
) lock_type,
DECODE (hk.lmode,
0, 'None',
1, 'NULL',
2, 'ROW-S (SS)',
3, 'ROW-X (SX)',
4, 'SHARE',
5, 'S/ROW-X (SSX)',
6, 'EXCLUSIVE',
TO_CHAR (hk.lmode)
) mode_held,
DECODE (wk.request,
0, 'None',
1, 'NULL',
2, 'ROW-S (SS)',
3, 'ROW-X (SX)',
4, 'SHARE',
5, 'S/ROW-X (SSX)',
6, 'EXCLUSIVE',
TO_CHAR (wk.request)
) mode_requested,
TO_CHAR (hk.id1) lock_id1, TO_CHAR (hk.id2) lock_id2,
DECODE
(hk.BLOCK,
0, 'NOT Blocking', /**//* Not blocking any other processes */
1, 'Blocking', /**//* This lock blocks other processes */
2, 'Global', /**//* This lock is global, so we can't tell */
TO_CHAR (hk.BLOCK)
) blocking_others
FROM v$lock hk, v$session bs, v$lock wk, v$session ws
WHERE hk.BLOCK = 1
AND hk.lmode != 0
AND hk.lmode != 1
AND wk.request != 0
AND wk.TYPE(+) = hk.TYPE
AND wk.id1(+) = hk.id1
AND wk.id2(+) = hk.id2
AND hk.SID = bs.SID(+)
AND wk.SID = ws.SID(+)
AND (bs.username IS NOT NULL)
AND (bs.username 'SYSTEM')
AND (bs.username 'SYS')
ORDER BY 1;
查询发生死锁的select语句
select sql_text from v$sql where hash_value in (
select sql_hash_value from v$session where sid in (select session_id from v$locked_object)
)