在执行drop user的时候，提示报错信息：ORA-01940: cannot drop a user that is currently connected

SQL> drop user ecity ;
ERROR at line 1:
ORA-01940: cannot drop a user that is currently connected

造成这个问题的原因是很明显的，有用户在连接，不允许drop掉该user。

解决方案：

首先查询一下数据中有没有用户在使用

select username,sid,serial#,paddr from v$session where username='ECITY';

USERNAME                                    SID    SERIAL# PADDR
------------------------------ ---------- -------------------------------------------------
ECITY                                       634        7   00000000C028D198

SQL> select PROGRAM from v$process where addr='00000000C028D198';

PROGRAM
----------------------------------------------------------------------------------------------------------
Oracle@oradb01 (DW00)

其次杀掉系统中的这个进程

SQL> alter system kill session '634,7';
System altered.

然后执行删除操作，即可完成

SQL> select saddr,sid,serial#,paddr,username,status from v$session where username is not null;
SQL> drop user ecity CASCADE;
User dropped.

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注：本文转自https://www.cnblogs.com/lwlxqlccc/p/8694696.html