自己在修改一张表的时候无法修改，报出一下错误： 系统正忙,但指定以nowait方式获取资源,或者超时失效
经查找是表被锁了，查看表被谁锁的方法如下：
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# FROM gv$session s, gv$lock l, dba_objects o WHERE l.sid = s.sid AND l.id1 = o.object_id(+) AND s.username is NOT NULL;
USERNAME LOCK_LEVEL OWNER OBJECT_NAME OBJECT_TYPE SID SERIAL#
--------- ----------------- ---------- ------------- ----------- ----- ----------
REPORT TABLE LOCK REPORT PRP_EMP TABLE 147 1366
断开他的session就可以执行了：
alter system kill session '147,1366';