关于lock的学习

系统中运行三个session，两个连接HR用户的用于测试lock，另一个为sys查看lock情况的，如下：

sys@ORCL112> select a.sid,a.type,a.lmode,a.request,a.block,trunc(a.id1/power(2,16)) rbs,bitand(a.id1,to_number('ffff','xxxx'))+0
lot,a.id2 from v$lock a,v$session b where a.sid=b.sid and b.username='HR';

       SID TY      LMODE    REQUEST      BLOCK        RBS       SLOT        ID2
---------- -- ---------- ---------- ---------- ---------- ---------- ----------
       200 AE          4          0          0          0        100          0
       200 TM          3          0          0          1       8397          0
       200 TX          6          0          0          8         20       1572

sys@ORCL112> select xidusn,xidslot,xidsqn,recursive from v$transaction;

    XIDUSN    XIDSLOT     XIDSQN REC
---------- ---------- ---------- ---
         8         20       1572 NO

sys@ORCL112> select xidusn,xidslot,xidsqn,recursive from v$transaction;

    XIDUSN    XIDSLOT     XIDSQN REC
---------- ---------- ---------- ---
         8         20       1572 NO
         2          3       1329 YES

sys@ORCL112> select a.sid,a.type,a.lmode,a.request,a.block,trunc(a.id1/power(2,16)) rbs,bitand(a.id1,to_number('ffff','xxxx'))+0
lot,a.id2 from v$lock a,v$session b where a.sid=b.sid and b.username='HR';

       SID TY      LMODE    REQUEST      BLOCK        RBS       SLOT        ID2
---------- -- ---------- ---------- ---------- ---------- ---------- ----------
       200 AE          4          0          0          0        100          0
       132 AE          4          0          0          0        100          0
       132 TX          0          6          0          8         20       1572
       200 TM          3          0          0          1       8397          0
       132 TM          3          0          0          1       8397          0
       200 TX          6          0          1          8         20       1572

已选择6行。

上述中
    XIDUSN    XIDSLOT     XIDSQN REC
---------- ---------- ---------- ---
         2          3       1329 YES
是什么？？（又测试两遍，再也没有出现两个事务的情况），什么情况下同张表多用户操作会出现多个事务？