Oracle中锁（lock）的用法

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_timeFROM v$locked_object l, all_objects o, v$session sWHERE l.object_id = o.object_idAND l.session_id = s.sidORDER 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.actionFROM v$sqlarea a, v$session s, v$locked_object lWHERE l.session_id = s.sidAND s.prev_sql_addr = a.addressORDER 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.TYPEFROM v$session s, v$lock lWHERE s.sid = l.sidAND s.username IS NOT NULLORDER 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.osuserFROM v$session s, v$lock l, dba_objects oWHERE l.sid = s.sidAND 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 sWHERE l.object_id = o.object_idAND l.session_id = s.sidORDER 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 bfrom v$lock, all_objectswhere sid > 6and v$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.processfrom v$locked_object a, v$session swhere 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。