Oracle中锁(lock)的用法
作者:springsnow
数据库锁介绍: https://www.jb51.net/article/248863.htm
一、查询oracle锁定的表:
1、锁相关表
- SELECT * FROM v$lock;
列:ADDR:锁定状态对象地址;KADDR:锁地址;SID :会话id;ID1:锁标识符#1;ID2:锁标识符#2;LMODE:会话持有的锁模式(0~6);REQUEST:进程请求的锁模式(0~6);
CTIME:当前模式的时间;BLOCK:为1代表阻碍者,表示正在阻碍其它会话; - SELECT * FROM v$locked_object;
- SELECT * FROM v$session;
- SELECT * FROM v$session_wait;
- SELECT * FROM v$sqlarea;
- SELECT * FROM v$process ;
- SELECT * FROM all_objects
2、常用语句
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$lock l WHERE s.sid = l.sid AND s.username IS NOT NULL ORDER BY sid;
4、这个语句将查找到数据库中所有的DML语句产生的锁,还可以发现,任何DML语句其实产生了两个锁,一个是表锁,一个是行锁。
SELECT /*+ rule */ s.username, DECODE(l.TYPE, 'TM', 'TABLE LOCK', 'TX', 'ROW LOCK', NULL) LOCK_LEVEL, o.owner, o.object_name, o.object_type, s.sid, s.serial#, s.terminal, s.machine, s.program, s.osuser FROM v$session s, v$lock l, dba_objects o WHERE l.sid = s.sid AND l.id1 = o.object_id(+) AND s.username IS NOT NULL;
5、如果发生了锁等待,我们可能更想知道是谁锁了表而引起谁的等待,以下的语句可以查询到谁锁了表,而谁在等待。
以下查询结果是一个树状结构,如果有子节点,则表示有等待发生。如果想知道锁用了哪个回滚段,还可以关联到V$rollname,其中xidusn就是回滚段的USN
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
3、kill session语句:
alter system kill session 'sid,serial#';
alter system kill session'494,7355';
二、一个有用查找脚本:
1、找到某表的锁 所属的sid,alter system kill session 'sid,serial#'
;即可
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;
2、查出被lock 的对象,然后 alter system kill session 'sid,serial#'
;
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;
三、LOCK TABLE
1、语法:
LOCK TABLE table_1 [,table_2, ..., table_n] IN lock_mode MODE NOWAIT
2、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
3、例子:
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
到此这篇关于Oracle锁(lock)的文章就介绍到这了。希望对大家的学习有所帮助,也希望大家多多支持脚本之家。