由于自己的粗心大意安装11Gr2 时，没有装SCOTT用户，执行脚本时执行错了，参照了“娜一片天空” 博客，的文章，成功删除，在此非常感谢。
原文http://wanwentao.blog.51cto.com/2406488/741550
ORA-01940: cannot drop a user that is currently connected
SQL> drop user scott cascade;
drop user scott cascade
*
ERROR at line 1:
ORA-01940: cannot drop a user that is currently connected
SQL> SELECT SID,SERIAL# FROM V$SESSION WHERE USERNAME='SCOTT';
SID SERIAL#
---------- ----------
49 4252
52 2158
SQL> ALTER SYSTEM KILL SESSION '49,4252';
System altered.
SQL> ALTER SYSTEM KILL SESSION '86,18117';
ALTER SYSTEM KILL SESSION '86,18117'
*
ERROR at line 1:
ORA-00030: User session ID does not exist.
SQL> ALTER SYSTEM KILL SESSION '52,2158';
System altered.
SQL> DROP USER SCOTT CASCADE;
User dropped.
SQL>