[20190522]DISABLE TABLE LOCK.txt
--//如果禁止table lock时,一些ddl操作会被禁止.但是我有点吃惊的是增加字段不受限制.
--//通过测试说明问题.
1.环境:
SCOTT@book> @ ver1
PORT_STRING VERSION BANNER
------------------------------ -------------- --------------------------------------------------------------------------------
x86_64/Linux 2.4.xx 11.2.0.4.0 Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
SCOTT@book> create table t as select rownum id from dual ;
Table created.
SCOTT@book> alter table t disable table lock;
Table altered.
2.测试:
SCOTT@book> truncate table t;
truncate table t
*
ERROR at line 1:
ORA-00069: cannot acquire lock -- table locks disabled for T
SCOTT@book> alter table t add v1 varchar2(10);
Table altered.
--//增加1列v1没有问题.
SCOTT@book> @ desc t
Name Null? Type
----- -------- ----------------------------
ID NUMBER
V1 VARCHAR2(10)
SCOTT@book> alter table t drop column v1;
alter table t drop column v1
*
ERROR at line 1:
ORA-00069: cannot acquire lock -- table locks disabled for T
--//删除列不行.
SCOTT@book> alter table t set unused column v1;
alter table t set unused column v1
*
ERROR at line 1:
ORA-00069: cannot acquire lock -- table locks disabled for T
3.继续:
SCOTT@book> alter table t enable table lock;
Table altered.
SCOTT@book> alter table t set unused column v1;
Table altered.
--//有时候感觉oracle设计的很奇怪,也就是增加1列不需要TM锁吗?
3.继续测试:即使有事务存在的情况下.
--//session 1:
SCOTT@book> @ spid
SID SERIAL# PROCESS SERVER SPID PID P_SERIAL# C50
---------- ---------- ------------------------ --------- ------ ------- ---------- --------------------------------------------------
30 535 42553 DEDICATED 42554 26 245 alter system kill session '30,535' immediate;
SCOTT@book> alter table t disable table lock;
Table altered.
--//session 2:
SCOTT@book> @ spid
SID SERIAL# PROCESS SERVER SPID PID P_SERIAL# C50
---------- ---------- ------------------------ --------- ------ ------- ---------- --------------------------------------------------
1 10297 43346 DEDICATED 43347 24 237 alter system kill session '1,10297' immediate;
SCOTT@book> insert into t values (2);
1 row created.
SCOTT@book> @ viewlock ;
SID SERIAL# USERNAME OSUSER MACHINE MODULE LOCK_TYPE MODE_HELD MODE_REQUE LOCK_ID1 LOCK_ID2 OWNER OBJECT_TYP OBJECT_NAME BLOCK LOCKWAIT
------ ---------- ---------- ---------- ---------- ------------ --------------- ---------- ---------- ---------- ---------- ------ ---------- -------------------- ----- --------------------
1 10297 SCOTT oracle gxqyydg4 SQL*Plus TX Transaction Exclusive None 655375 4583723 No
--//session 1:
SCOTT@book> alter table t add v1 varchar2(10);
Table altered.
SCOTT@book> alter table t add v2 varchar2(10);
Table altered.
--//确实可以.
--//session 2:
SCOTT@book> select * from t;
ID V1 V2
---------- ---------- ----------
1
2
SCOTT@book> insert into t values (3);
insert into t values (3)
*
ERROR at line 1:
ORA-00947: not enough values
--//增加了字段.
SCOTT@book> insert into t values (3,'a','b');
1 row created.
SCOTT@book> select * from t;
ID V1 V2
---------- ---------- ----------
1
2
3 a b
4.如果enable table lock,如果有会话事务没有提交,在别的会话增加一列一定会挂起:
--//感觉oracle的设计还真奇怪....
--//session 1:
SCOTT@book> alter table t enable table lock;
Table altered.
--//session 2:
SCOTT@book> insert into t values (4,'a','b');
1 row created.
--//session 1:
SCOTT@book> alter table t add v3 varchar2(10);
--//挂起!!
SCOTT@book> @ viewlock
SID SERIAL# USERNAME OSUSER MACHINE MODULE LOCK_TYPE MODE_HELD MODE_REQUE LOCK_ID1 LOCK_ID2 OWNER OBJECT_TYP OBJECT_NAME BLOCK LOCKWAIT
------ ---------- ---------- ---------- ---------- ------------ --------------- ---------- ---------- ---------- ---------- ------ ---------- -------------------- ----- --------------------
1 10297 SCOTT oracle gxqyydg4 SQL*Plus TM DML(TM) Row-X (SX) None 42044813 0 SCOTT TABLE T No
1 10297 SCOTT oracle gxqyydg4 SQL*Plus TX Transaction Exclusive None 655379 4583660 Yes
30 535 SCOTT oracle gxqyydg4 SQL*Plus TX Transaction None Share 655379 4583660 No 0000000085439E00
30 535 SCOTT oracle gxqyydg4 SQL*Plus TM DML(TM) Row-X (SX) None 42044813 0 SCOTT TABLE T No 0000000085439E00
30 535 SCOTT oracle gxqyydg4 SQL*Plus TX Transaction Exclusive None 589849 212173 No 0000000085439E00
5.viewlock.sql脚本:
$ cat viewlock.sql
column sid format 99999
column username format a10
column osuser format a10
column machine format a10
column lock_type format a15
column mode_held format a10
column mode_requested format a10
column lock_id1 format a10
column lock_id2 format a10
column owner format a6
column object_type format a10
column object_name format a20
column block format a5
column lockwait format a20
SELECT se.SID, se.serial#,se.username, se.osuser, se.machine,se.module,
DECODE (lk.TYPE, 'TX', 'TX Transaction', 'TM', 'TM DML(TM)', 'UL', 'PL/SQL User Lock', lk.TYPE) lock_type,
DECODE (lk.lmode,
0, 'None',
1, 'Null',
2, 'Row-S (SS)',
3, 'Row-X (SX)',
4, 'Share',
5, 'S/Row-X (SSX)',
6, 'Exclusive',
TO_CHAR (lk.lmode)
) mode_held,
DECODE (lk.request,
0, 'None',
1, 'Null',
2, 'Row-S (SS)',
3, 'Row-X (SX)',
4, 'Share',
5, 'S/Row-X (SSX)',
6, 'Exclusive',
TO_CHAR (lk.request)
) mode_requested,
TO_CHAR (lk.id1) lock_id1, TO_CHAR (lk.id2) lock_id2, ob.owner, ob.object_type, ob.object_name,
DECODE (lk.BLOCK, 0, 'No', 1, 'Yes', 2, 'Global') BLOCK, se.lockwait
FROM v$lock lk, dba_objects ob, v$session se
WHERE lk.TYPE IN ('TX','TM', 'UL') AND lk.SID = se.SID AND lk.id1 = ob.object_id(+) order by 1;