Oracle的锁表与解锁

Oracle的锁表与解锁

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

--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
alter system kill session 'sid,serial#'

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                                                           /*+ rule */
        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