SQL> drop user DCS_LIVE cascade; drop user DCS_LIVE cascade * ERROR at line 1: ORA-01940: cannot drop a user that is currently connected Solution of The Problem: Find out the connected user sid and serial# by, SQL> select sid, serial# from v$session where username = 'DCS_LIVE'; SID SERIAL# ---------- ---------- 268 1268 315 1223 Before killing session you may wish to lock the account for further connection attempts. This is extremely necessary to drop a user who automatically establish session like to drop an application user or to drop a user who perform batch jobs. SQL> Alter user DCS_LIVE account lock; Now kill the connected session. SQL> alter system kill session '268,1268'; System altered. SQL> alter system kill session '315,1223'; System altered. And then drop the user. SQL> drop user DCS_LIVE cascade; User dropped.