TM 表锁，发生在insert,update,delete以及select for update操作时，目的是保证操作能够正常进行，并且阻止其它人对表执行DDL操作。
TM锁几种模式的互斥关系图:
在巡检期间，检查如果发现有相关的session_wait锁，可按以下步骤查找相应的锁
1. 使用V$LOCK找出session持有的锁。
2. 使用V$SESSION找出持有锁或等待锁的session执行的sql语句。
3. 使用V$SESSION_WAIT找出什么原因导致session持有锁堵塞。
4. 使用V$SESSION获取关于持有锁的程序和用户的更多信息。
V$LOCK中的常用列
SID：表示持有锁的会话信息。
TYPE：表示锁的类型。值包括TM和TX等。
LMODE：表示会话等待的锁模式的信息。用数字0－6表示，和表1相对应。
REQUEST：表示session请求的锁模式的信息。
ID1,ID2：表示锁的对象标识。
例如：首先查出当前TM','TX等待事件的等待会话
BYS@ bys3>select a.sid,a.kaddr,a.addr,a.type,a.id1,a.id2,a.lmode,a.request,a.block from v$lock a where a.type in('TM','TX') order by 1,2;
SID KADDR ADDR TY ID1 ID2 LMODE REQUEST BLOCK
---------- -------- -------- -- ---------- ---------- ---------- ---------- ----------
1 B693D590 B693D560 TM 22326 0 0 3 0
44 B693D590 B693D560 TM 22326 0 5 0
BYS@ bys3>select sql_id from v$session where sid=1; 通过上一步会话SID，查出1号会话当前在等待的语句
SQL_ID
-------------
01mv5v746cfbq
BYS@ bys3>select * from v$sqltext where sql_id='01mv5v746cfbq'; --通过上一步查出SQL_SID，查出SQL_TEXT
ADDRESS HASH_VALUE SQL_ID COMMAND_TYPE PIECE SQL_TEXT
-------- ---------- ------------- ------------ ---------- ------------------------------
25DDD5FC 3362142582 01mv5v746cfbq 6 0 update test set status=8899
用一条语句来查询是：select a.*,b.sid,b.username from v$sqltext a,v$session b,v$lock c where a.sql_id=b.sql_id and b.sid=c.sid and c.type in('TM','TX');
详见：v$session/v$process视图涉及的相关会话信息的查询
1.环境准备：--有些实验数据是后来补充的，可能不太一致。
BYS@ bys001>select distinct sid from v$mystat;
SID
----------
19
BYS@ bys001>select * from test;
no rows selected
BYS@ bys001>insert into test values(1);
1 row created.
BYS@ bys001>commit;
Commit complete.
BYS@ bys001>select * from test;
A
----------
1
BYS@ bys001>select sid,type,id1,id2,lmode,request,block from v$lock where type in('TM','TX') order by 1,2;
no rows selected
TM锁1号锁实验：
create table order_info(customerid number);
CREATE OR REPLACE PROCEDURE kzcz214001 (cust_id in NUMBER)
AS
BEGIN
insert into order_info values(cust_id);
commit;
END;
/
col owner for a10
col name for a10
col type for a10
select SESSION_ID sid,OWNER,NAME,Type,MODE_HELD held,MODE_REQUESTED request from dba_ddl_locks WHERE NAME='KZCZ214001';
这一句查询dba_ddl_locks表，如果手工建库，dba_ddl_locks表可能不存在，需要SYS用户运行脚本去创建：?/rdbms/admin/catblock.sql
exec kzcz214001(1);
BYS@ bys3>select SESSION_ID sid,OWNER,NAME,Type,MODE_HELD held,MODE_REQUESTED request from dba_ddl_locks WHERE NAME='KZCZ214001';
SID OWNER NAME TYPE HELD REQUEST
---------- ---------- ---------- ---------- --------- ---------
1 BYS KZCZ214001 Table/Proc Null None
edure/Type
BYS@ bys3>select status from dba_objects where object_name='KZCZ214001';
STATUS
-------
VALID
BYS@ bys3>alter table order_info add(name varchar2(10));
Table altered.
BYS@ bys3>select status from dba_objects where object_name='KZCZ214001';
STATUS
-------
INVALID
索引失效后，1号锁还能查到。。。
BYS@ bys3>select SESSION_ID sid,OWNER,NAME,Type,MODE_HELD held,MODE_REQUESTED request from dba_ddl_locks WHERE NAME='KZCZ214001';
SID OWNER NAME TYPE HELD REQUEST
---------- ---------- ---------- ---------- --------- ---------
1 BYS KZCZ214001 Table/Proc Null None
edure/Type
####################################
等级共享锁 2 row share----rs
产生2号TM锁方法1：--手动锁定
把在19会话将test表设置为等级共享锁模式
BYS@ bys001>lock table test in row share mode;
Table(s) Locked.
可以查询到是在test表加了个模式2的锁
BYS@ bys001>select sid,type,id1,id2,lmode,request,block from v$lock where type in('TM','TX') order by 1,2;
SID TY ID1 ID2 LMODE REQUEST BLOCK
---------- -- ---------- ---------- ---------- ---------- ----------
19 TM 77389 0 2 0 0
BYS@ bys001>select object_name from dba_objects where object_id=77389;
OBJECT_NAME
-------------------------------
TEST
在另一个会话147上做DML操作：
BYS@ bys001>select distinct sid from v$mystat;
SID
----------
147
BYS@ bys001>insert into test values(2);
1 row created.
BYS@ bys001>delete from test where a=1;
1 row deleted.
BYS@ bys001>select * from test;
A
----------
2
BYS@ bys001>update test set a=22 where a=2;
1 row updated.
BYS@ bys001>select * from test;
A
----------
22
在会话19上查询：
BYS@ bys001>select sid,type,id1,id2,lmode,request,block from v$lock where type in('TM','TX') order by 1,2;
SID TY ID1 ID2 LMODE REQUEST BLOCK
---------- -- ---------- ---------- ---------- ---------- ----------
19 TM 77389 0 2 0 0
147 TM 77389 0 3 0 0
147 TX 196621 28393 6 0 0
如果使用DML语句，会报错：ORA-00054: resource busy and acquire with NOWAIT specified or timeout expired
产生2号TM锁方法2：--大表在线建索引
在会话1：--在大表上在线创建索引，要用ONLINE，不用ONLINE不会有2号锁。
BYS@ bys3>create index idx_test1 on test1(id) online;
Index created.
会话2：--有4号锁和2号锁
BYS@ bys3>select * from v$lock where sid=1;
ADDR KADDR SID TY ID1 ID2 LMODE REQUEST CTIME BLOCK
-------- -------- ---------- -- ---------- ---------- ---------- ---------- ---------- ----------
2AD66694 2AD666C0 1 AE 100 0 4 0 2154 0
2AD6697C 2AD669A8 1 DL 22325 0 3 0 4 0
2AD66AF0 2AD66B1C 1 OD 22325 0 4 0 4 0
2AD66C64 2AD66C90 1 DL 22325 0 3 0 4 0
B6A0DB98 B6A0DBC8 1 TM 22325 0 2 0 4 0
B6A0DB98 B6A0DBC8 1 TM 22354 0 4 0 4 0
2926D618 2926D690 1 TS 4 16777362 6 0 2 0
28471AE4 28471B24 1 TX 327696 2557 6 0
BYS@ bys3>col object_name for a20
BYS@ bys3>select a.sid,a.type,a.lmode,a.request,b.object_name from v$lock a,dba_objects b where a.id1=b.object_id and sid=1;
SID TY LMODE REQUEST OBJECT_NAME
---------- -- ---------- ---------- --------------------
1 TM 2 0 TEST1
1 TM 4 0 SYS_JOURNAL_22360
1 AE 4 0 ORA$BASE
1 OD 4 0 TEST1
1 DL 3 0 TEST1
1 DL 3 0 TEST1
小结：行级共享锁，是限制最少的TM锁，可以提供最高程度的并发性。其他会话可以对锁定的表进行任何类型的DML操作，还可以与其他会话锁并存。
################################################################################
等级排他锁 row exclusive table lock---RX 3
BYS@ bys001>select distinct sid from v$mystat;
SID
----------
19
BYS@ bys001>lock table test in row exclusive mode;
Table(s) Locked.
BYS@ bys001>select sid,type,id1,id2,lmode,request,block from v$lock where type in('TM','TX') order by 1,2;
SID TY ID1 ID2 LMODE REQUEST BLOCK
---------- -- ---------- ---------- ---------- ---------- ----------
19 TM 77389 0 3 0 0
3级锁是一个灵活性比较大的锁，insert delete update，for update 都可以产生一个3级锁，也允许其他事务来修改锁定的表
BYS@ bys001>select * from test;
A
----------
22
BYS@ bys001>update test set a=99 where a=22;
1 row updated.
BYS@ bys001>select * from test;
A
----------
99
BYS@ bys001>select distinct sid from v$mystat;
SID
----------
147
BYS@ bys001>insert into test values(55);
1 row created.
BYS@ bys001>select * from test;
A
----------
22
55
BYS@ bys001>select sid,type,id1,id2,lmode,request,block from v$lock where type in('TM','TX') order by 1,2;
SID TY ID1 ID2 LMODE REQUEST BLOCK
---------- -- ---------- ---------- ---------- ---------- ----------
19 TM 77389 0 3 0 0
19 TX 655390 28214 6 0 0
147 TM 77389 0 3 0 0
147 TX 589824 28423 6 0 0
block列全部是0,没有阻塞。
此时，如执行DDL语句，报错：ORA-00054:resource busy and acquire with NOWAIT specified or timeout expired
小结：行级排他锁，通常已经有事务在修改行或者select…for update 修改结果集。允许其他事务对锁定的表进行select insert update delete 或 lock table 同时锁定一张表。
#####################################################################################
共享锁 share table lock 4
BYS@ bys001>select distinct sid from v$mystat;
SID
----------
19
BYS@ bys001>select * from test;
A
----------
99
55
BYS@ bys001>lock table test in row share mode;
Table(s) Locked.
BYS@ bys001>select sid,type,id1,id2,lmode,request,block from v$lock where type in('TM','TX') order by 1,2;
SID TY ID1 ID2 LMODE REQUEST BLOCK
---------- -- ---------- ---------- ---------- ---------- ----------
19 TM 77389 0 3 0 0
19 TX 655390 28214 6 0 0
模式标识：4
4级锁禁止其他会话对锁定的表进行DML操作但可以select查询，还允许多个事物一起持有
在会话147上进行删除操作，
BYS@ bys001>select distinct sid from v$mystat;
SID
----------
147
BYS@ bys001>DELETE TEST ;
BYS@ bys001>select sid,type,id1,id2,lmode,request,block from v$lock where type in('TM','TX') order by 1,2;
SID TY ID1 ID2 LMODE REQUEST BLOCK
---------- -- ---------- ---------- ---------- ---------- ----------
19 TM 77389 0 3 0 0
19 TX 655390 28214 6 0 1
147 TM 77389 0 3 0 0
147 TX 655390 28214 0 6 0
BYS@ bys001>lock table test in share mode;
Table(s) Locked.
BYS@ bys001>select sid,type,id1,id2,lmode,request,block from v$lock where type in('TM','TX') order by 1,2;
SID TY ID1 ID2 LMODE REQUEST BLOCK
---------- -- ---------- ---------- ---------- ---------- ----------
19 TM 77389 0 4 0 0
BYS@ bys001>select sid,type,id1,id2,lmode,request,block from v$lock where type in('TM','TX') order by 1,2;
SID TY ID1 ID2 LMODE REQUEST BLOCK
---------- -- ---------- ---------- ---------- ---------- ----------
19 TM 77389 0 4 0 1
147 TM 77389 0 0 3 0
共享锁，其它事务可以查询锁定的表但不能修改，只允许当前事务修改，但可以多个事务持有它。
另一个产生4号锁的，见： --2号锁在线建索引实验。
##########################################################
TM锁5号锁实验：
BYS@ bys001>lock table test in share row exclusive mode;
Table(s) Locked.
BYS@ bys001>select sid,type,id1,id2,lmode,request,block from v$lock where type in('TM','TX') order by 1,2;
SID TY ID1 ID2 LMODE REQUEST BLOCK
---------- -- ---------- ---------- ---------- ---------- ----------
19 TM 77389 0 5 0 0
BYS@ bys001>select * from test;
no rows selected
BYS@ bys001>select sid,type,id1,id2,lmode,request,block from v$lock where type in('TM','TX') order by 1,2;
SID TY ID1 ID2 LMODE REQUEST BLOCK
---------- -- ---------- ---------- ---------- ---------- ----------
19 TM 77389 0 5 0 0
BYS@ bys001>insert into test values(88);
1 row created.
BYS@ bys001>select sid,type,id1,id2,lmode,request,block from v$lock where type in('TM','TX') order by 1,2;
SID TY ID1 ID2 LMODE REQUEST BLOCK
---------- -- ---------- ---------- ---------- ---------- ----------
19 TM 77389 0 5 0 0
19 TX 524320 28676 6 0 0
在147会话执行DML操作会hang住
BYS@ bys001>insert into test values(88);
此时查询
BYS@ bys001>select sid,type,id1,id2,lmode,request,block from v$lock where type in('TM','TX') order by 1,2;
SID TY ID1 ID2 LMODE REQUEST BLOCK
---------- -- ---------- ---------- ---------- ---------- ----------
19 TM 77389 0 5 0 1
19 TX 524320 28676 6 0 0
147 TM 77389 0 0 3 0
小结：共享行级排他锁，同一时间只允许一个事务持有和修改锁定的表，其他事务可以查询但不能修改。
5号锁--在存储过程运行中会出现：A B两个会话同时执行同一个存储过程时
session A exec p
session B exec p
#############################################
TM锁6号锁实验：
BYS@ bys001>lock table test in exclusive mode;
Table(s) Locked.
BYS@ bys001>select sid,type,id1,id2,lmode,request,block from v$lock where type in('TM','TX') order by 1,2;
SID TY ID1 ID2 LMODE REQUEST BLOCK
---------- -- ---------- ---------- ---------- ---------- ----------
19 TM 77389 0 6 0 0
在会话147进行hang住
BYS@ bys001>lock table test in row share mode; ---在此HANG住
BYS@ bys001>select sid,type,id1,id2,lmode,request,block from v$lock where type in('TM','TX') order by 1,2;
SID TY ID1 ID2 LMODE REQUEST BLOCK
---------- -- ---------- ---------- ---------- ---------- ----------
19 TM 77389 0 6 0 1
147 TM 77389 0 0 2 0
