ORA-01940: cannot drop a user that is currently connected :


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


    SQL> select sid,serial# ,username from v$session where username like '%AND%';
           SID    SERIAL# USERNAME
    ---------- ---------- ------------------------------
           745        821 ANDY

    SQL> alter system kill session '745,821' immediate ;
    System altered.


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

Solution is :

    SQL> startup force restrict;
    ORACLE instance started.
    Total System Global Area 7686086656 bytes
    Fixed Size                  2228032 bytes
    Variable Size            1811939520 bytes
    Database Buffers         5729419264 bytes
    Redo Buffers              142499840 bytes
    Database mounted.
    Database opened.


     SQL> drop user ANDY cascade ;
    User dropped.