分类: Oracle
2010-03-24 08:53:22
总结1:Oracle的锁表与解锁
SELECT s.username,
DECODE (l.TYPE, 'tm', 'table lock', 'tx', 'row lock', NULL)
lock_level,
o.owner,
o.object_name,
o.object_type,
s.sid,
s.serial#,
s.terminal,
s.machine,
s.program,
s.osuser
FROM v$session s, v$lock l, dba_objects o
WHERE l.sid = s.sid AND l.id1 = o.object_id(+) AND s.username IS NOT NULL;
--kill session语句
alter system kill session'50,492';
--以下几个为相关表
SELECT * FROM v$lock;
SELECT * FROM v$sqlarea;
SELECT * FROM v$session;
SELECT * FROM v$process ;
SELECT * FROM v$locked_object;
SELECT * FROM all_objects;
SELECT * FROM v$session_wait;
--1.查出锁定object的session的信息以及被锁定的object名
SELECT l.session_id sid,
s.serial#,
l.locked_mode,
l.oracle_username,
l.os_user_name,
s.machine,
s.terminal,
o.object_name,
s.logon_time
FROM v$locked_object l, all_objects o, v$session s
WHERE l.object_id = o.object_id AND l.session_id = s.sid
ORDER BY sid, s.serial#;
--2.查出锁定表的session的sid, serial#,os_user_name, machine name, terminal和执行的语句
--比上面那段多出sql_text和action
SELECT l.session_id sid,
s.serial#,
l.locked_mode,
l.oracle_username,
s.user#,
l.os_user_name,
s.machine,
s.terminal,
a.sql_text,
a.action
FROM v$sqlarea a, v$session s, v$locked_object l
WHERE l.session_id = s.sid AND s.prev_sql_addr = a.address
ORDER BY sid, s.serial#;
--3.查出锁定表的sid, serial#,os_user_name, machine_name, terminal,锁的type,mode
SELECT s.sid,
s.serial#,
s.username,
s.schemaname,
s.osuser,
s.process,
s.machine,
s.terminal,
s.logon_time,
l.TYPE
FROM v$session s, v$lock l
WHERE s.sid = l.sid AND s.username IS NOT NULL
ORDER BY sid;
这个语句将查找到数据库中所有的DML语句产生的锁,还可以发现,
任何DML语句其实产生了两个锁,一个是表锁,一个是行锁。
杀锁命令
SELECT /*+ rule */
s .username,
DECODE (l.TYPE, 'TM', 'TABLE LOCK', 'TX', 'ROW LOCK', NULL)
LOCK_LEVEL,
o.owner,
o.object_name,
o.object_type,
s.sid,
s.serial#,
s.terminal,
s.machine,
s.program,
s.osuser
FROM v$session s, v$lock l, dba_objects o
WHERE l.sid = s.sid AND l.id1 = o.object_id(+) AND s.username IS NOT NULL;
如果发生了锁等待,我们可能更想知道是谁锁了表而引起谁的等待
以下的语句可以查询到谁锁了表,而谁在等待。
以上查询结果是一个树状结构,如果有子节点,则表示有等待发生。
如果想知道锁用了哪个回滚段,还可以关联到V$rollname,其中xidusn就是回滚段的USN
col user_name format a10
col owner format a10
col object_name format a10
col object_type format a10
SELECT LPAD (' ', DECODE (l.xidusn, 0, 3, 0)) || l.oracle_username
user_name,
o.owner,
o.object_name,
o.object_type,
s.sid,
s.serial#
FROM v$locked_object l, dba_objects o, v$session s
WHERE l.object_id = o.object_id AND l.session_id = s.sid
ORDER BY o.object_id, xidusn DESC
总结2:一个有用查找脚本:
column sid format 999;
column b format 9;
column object_name format a30;
column locktype format a20;
select v$lock.sid,
decode(v$lock.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 Invalida-tion',
'LS', 'Log Start or Switch',
'RW', 'Row Wait',
'SQ', 'Sequence Number',
'TE', 'Extend Table',
'TT', 'Temp Table',
'Unknown') LockType,
rtrim(owner) || '.' || object_name object_name,
decode(lmode, 0, 'None',
1, 'Null',
2, 'Row-S',
3, 'Row-X',
4, 'Share',
5, 'S/Row-X',
6, 'Exclusive','Unknown') LockMode,
decode(request, 0, 'None',
1, 'Null',
2, 'Row-S',
3, 'Row-X',
4, 'Share',
5, 'S/Row-X',
6, 'Exclusive', 'Unknown') RequestMode,
ctime, block b
from v$lock, all_objects
where sid > 6
and v$lock.id1 = all_objects.object_id;
找到某表的锁 所属的sid.
alter system kill session 'sid,serial#';
即可
select object_id,session_id,serial#,oracle_username,os_user_name,s.process
from v$locked_object a,v$session s
where a.session_id=s.sid;
查出被lock 的对象
然后 alter system kill session 'sid,serial#';
知识点3:
LOCK TABLE
语法:
LOCK TABLE table_1 [,table_2, ..., table_n] IN lock_mode MODE
NOWAIT
变量:
table_1,...,table_n: 一系列你想通过使用LOCK TABLE语句锁住的数据库表。
lock_mode: 对于某一数据库表你要设定的锁定模式。你可以从如下的锁定模式中任选一个。
EXCLUSIVE
SHARE ROW EXCLUSIVE
SHARE
SHARE UPDATE
ROW SHARE
ROW EXCLUSIVE
NOWAIT: Oracle will not wait to lock the given Table(s), if the Table(s) is(are) not
available
例子:
SQL
LOCK TABLE loan IN SHARE MODE ;
LOCK TABLE region IN EXCLUSIVE MODE NOWAIT;
LOCK TABLE acct IN SHARE UPDATE MODE;
LOCK TABLE bank IN ROW EXCLUSIVE MODE NOWAIT;
LOCK TABLE user IN SHARE ROW EXCLUSIVE MODE;
LOCK TABLE branch IN ROW SHARE MODE NOWAIT;
commit
/