Dropping connected users in Oracle database

Users are all capitals in v$session (and data dictionary views). If you match with capitals you should find your session to kill.

SELECT s.sid, s.serial#, s.status, p.spid 
  FROM v$session s, v$process p 
 WHERE s.username = 'TEST' --<<<--
  AND p.addr(+) = s.paddr
 /

Pass actual SID and SERIAL# values for user TEST then drop user...:

ALTER SYSTEM KILL SESSION '<SID>, <SERIAL>'
/

Solution :

login as sysdaba:

sqlplus  / as sysdba

then:

sql>Shutdown immediate;

sql>startup restrict;

sql>drop user TEST cascade;

If you want to re-activate DB normally either reset the server or :

sql>Shutdown immediate;

sql>startup;

:)

Issue has been fixed using below procedure :

DECLARE
  v_user_exists NUMBER;
  user_name CONSTANT varchar2(20) := 'SCOTT';
BEGIN
  LOOP
    FOR c IN (SELECT s.sid, s.serial# FROM v$session s WHERE upper(s.username) = user_name)
    LOOP
      EXECUTE IMMEDIATE
        'alter system kill session ''' || c.sid || ',' || c.serial# || ''' IMMEDIATE';
    END LOOP;
    BEGIN
      EXECUTE IMMEDIATE 'drop user ' || user_name || ' cascade';
      EXCEPTION WHEN OTHERS THEN
      IF (SQLCODE = -1940) THEN
        NULL;
      ELSE
        RAISE;
      END IF;
    END;
    BEGIN
      SELECT COUNT(*) INTO v_user_exists FROM dba_users WHERE username = user_name;
      EXIT WHEN v_user_exists = 0;
    END;
  END LOOP;
END;
/