About transaction lock and V$lock view

你大概习惯了日常检视v$lock视图，了解实例中的锁定了阻塞情况，v$lock是一个非常有用的视图，每个dba都爱用他，我们来看看下面的例子:

SQL> drop table youyus;

Table dropped

SQL> create table youyus as select rownum t1 from dual connect by level<=100;

Table created
 /*首先清理环境*/
session 134:
SQL> update youyus set t1=t1+1 where t1>50;

50 rows updated
/*session 134 更新了表中t1>50的行*/

session 131:
SQL> update youyus set t1=t1+1;

/*session 131 试图更新表中所有记录，但因为表中部分行仍被锁定着，故处于等待状态*/

SQL> select * from v$lock where sid in (134,131) and type in ('TM','TX') order by SID,TYPE;

ADDR     KADDR           SID TYPE        ID1        ID2      LMODE    REQUEST      CTIME      BLOCK
-------- -------- ---------- ---- ---------- ---------- ---------- ---------- ---------- ----------
0DD76430 0DD76460        131 TM        73547          0          3          0        802          0
2DE665B8 2DE665F8        131 TX       196619        878          6          0        802          0
2EF45F00 2EF45F2C        131 TX       262166        693          0          6        802          0
0DD76430 0DD76460        134 TM        73547          0          3          0        813          0
2DE36D04 2DE36D44        134 TX       262166        693          6          0        813          1