Oracle中鎖（lock）的用法
數(shù)據(jù)庫(kù)鎖介紹： https://www.jb51.net/article/248863.htm
一、查詢oracle鎖定的表：
1、鎖相關(guān)表
- SELECT * FROM v$lock;
列：ADDR:鎖定狀態(tài)對(duì)象地址;KADDR:鎖地址;SID :會(huì)話id;ID1:鎖標(biāo)識(shí)符#1;ID2:鎖標(biāo)識(shí)符#2;LMODE:會(huì)話持有的鎖模式（0~6）;REQUEST:進(jìn)程請(qǐng)求的鎖模式（0~6）;
CTIME:當(dāng)前模式的時(shí)間;BLOCK:為1代表阻礙者，表示正在阻礙其它會(huì)話; - SELECT * FROM v$locked_object;
- SELECT * FROM v$session;
- SELECT * FROM v$session_wait;
- SELECT * FROM v$sqlarea;
- SELECT * FROM v$process ;
- SELECT * FROM all_objects
2、常用語(yǔ)句
1、查出鎖定object的session的信息以及被鎖定的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、查出鎖定表的session的sid, serial#,os_user_name, machine name, terminal和執(zhí)行的語(yǔ)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$locked_object l WHERE l.session_id = s.sid AND s.prev_sql_addr = a.address ORDER BY sid, s.serial#;
3、查出鎖定表的sid, serial#,os_user_name, machine_name, terminal，鎖的type,mode
SELECT s.sid, s.serial#, s.username, s.schemaname, s.osuser, s.process, s.machine, s.terminal, s.logon_time, l.TYPE FROM v$session s, v$lock l WHERE s.sid = l.sid AND s.username IS NOT NULL ORDER BY sid;
4、這個(gè)語(yǔ)句將查找到數(shù)據(jù)庫(kù)中所有的DML語(yǔ)句產(chǎn)生的鎖，還可以發(fā)現(xiàn)，任何DML語(yǔ)句其實(shí)產(chǎn)生了兩個(gè)鎖，一個(gè)是表鎖，一個(gè)是行鎖。
SELECT /*+ rule */ s.username, DECODE(l.TYPE, 'TM', 'TABLE LOCK', 'TX', 'ROW LOCK', NULL) LOCK_LEVEL, o.owner, o.object_name, o.object_type, s.sid, s.serial#, s.terminal, s.machine, s.program, s.osuser FROM v$session s, v$lock l, dba_objects o WHERE l.sid = s.sid AND l.id1 = o.object_id(+) AND s.username IS NOT NULL;
5、如果發(fā)生了鎖等待，我們可能更想知道是誰(shuí)鎖了表而引起誰(shuí)的等待,以下的語(yǔ)句可以查詢到誰(shuí)鎖了表，而誰(shuí)在等待。
以下查詢結(jié)果是一個(gè)樹(shù)狀結(jié)構(gòu)，如果有子節(jié)點(diǎn)，則表示有等待發(fā)生。如果想知道鎖用了哪個(gè)回滾段，還可以關(guān)聯(lián)到V$rollname，其中xidusn就是回滾段的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 DESC3、kill session語(yǔ)句：
alter system kill session 'sid,serial#';
alter system kill session'494,7355';
二、一個(gè)有用查找腳本：
1、找到某表的鎖 所屬的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 的對(duì)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、語(yǔ)法：
LOCK TABLE table_1 [,table_2, ..., table_n] IN lock_mode MODE NOWAIT
2、變量：
table_1,...,table_n: 一系列你想通過(guò)使用LOCK TABLE語(yǔ)句鎖住的數(shù)據(jù)庫(kù)表。
lock_mode: 對(duì)于某一數(shù)據(jù)庫(kù)表你要設(shè)定的鎖定模式。你可以從如下的鎖定模式中任選一個(gè)。
- 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
到此這篇關(guān)于Oracle鎖（lock）的文章就介紹到這了。希望對(duì)大家的學(xué)習(xí)有所幫助，也希望大家多多支持本站。
版權(quán)聲明：本站文章來(lái)源標(biāo)注為YINGSOO的內(nèi)容版權(quán)均為本站所有，歡迎引用、轉(zhuǎn)載，請(qǐng)保持原文完整并注明來(lái)源及原文鏈接。禁止復(fù)制或仿造本網(wǎng)站，禁止在非www.sddonglingsh.com所屬的服務(wù)器上建立鏡像，否則將依法追究法律責(zé)任。本站部分內(nèi)容來(lái)源于網(wǎng)友推薦、互聯(lián)網(wǎng)收集整理而來(lái)，僅供學(xué)習(xí)參考，不代表本站立場(chǎng)，如有內(nèi)容涉嫌侵權(quán)，請(qǐng)聯(lián)系alex-e#qq.com處理。
關(guān)注官方微信