[oracle] Dropping connected users in Oracle database

I want to drop some users in Oracle DB using sqlplus but I am getting error:

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

I followed the link in SO to find out the sessions - Dropping a connected user from an Oracle 10g database schema

But when I ran the command I am not getting any results:

SQL> select sid,serial# from v$session where username = 'test';

no rows selected

Please help me how to drop users in this case.

If you use RAC then you need to use GV$* views instead V$*. Try to find your session by

select * from gv$session where username = 'test';

and then you can kill the session by

alter system kill session 'sid, serial#, @inst_id' immediate;

I was trying to follow the flow described here - but haven't luck to completely kill the session.. Then I fond additional step here:
http://wyding.blogspot.com/2013/08/solution-for-ora-01940-cannot-drop-user.html

What I did:
1. select 'alter system kill session ''' || sid || ',' || serial# || ''';' from v$session where username = '<your_schema>'; - as described below.
Out put will be something like this:
alter system kill session '22,15' immediate;
2. alter system disconnect session '22,15' IMMEDIATE ; - 22-sid, 15-serial - repeat the command for each returned session from previous command
3. Repeat steps 1-2 while select... not return an empty table
4. Call drop user...

What was missed - call alter system disconnect session '22,15' IMMEDIATE ; for each of session returned by select 'alter system kill session '..

Basically I believe that killing all sessions should be the solution, but...

I found similar discussion - https://community.oracle.com/thread/1054062 to my problem and that was I had no sessions for that users, but I still received the error. I tried also second the best answer:

sql>Shutdown immediate;

sql>startup restrict;

sql>drop user TEST cascade;

What worked for me at the end was to login as the user, drop all tables manually - select for creating drop statements is

select 'drop table ' || TABLE_NAME || ';'  from user_tables;

(Needs to be re-run several times because of references)

I have no idea how is that related, I dropped also functions and sequences (because that was all I had in schema)

When I did that and I logged off, I had several sessions in v$session table and when I killed those I was able to drop user.

My DB was still started in restricted mode (not sure if important or not).

Might help someone else.

BTW: my Oracle version is Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production

go to services in administrative tools and select oracleserviceSID and restart it

I had the same problem, Oracle config in default affects letter register. In exact my Scheme_Name was written all Capital letters. You can see your Scheme_Name on "Other Users" tab, if you are using Oracle S

Here's how I "automate" Dropping connected users in Oracle database:

# A shell script to Drop a Database Schema, forcing off any Connected Sessions (for example, before an Import) 
# Warning! With great power comes great responsibility.
# It is often advisable to take an Export before Dropping a Schema

if [ "$1" = "" ] 
then
    echo "Which Schema?"
    read schema
else
    echo "Are you sure? (y/n)"
    read reply
    [ ! $reply = y ] && return 1
    schema=$1
fi

sqlplus / as sysdba <<EOF
set echo on
alter user $schema account lock;
-- Exterminate all sessions!
begin     
  for x in ( select sid, serial# from v\$session where username=upper('$schema') )
  loop  
   execute immediate ( 'alter system kill session '''|| x.Sid || ',' || x.Serial# || ''' immediate' );  
  end loop;  
  dbms_lock.sleep( seconds => 2 ); -- Prevent ORA-01940: cannot drop a user that is currently connected
end;
/
drop user $schema cascade;
quit
EOF

Do a query:

SELECT * FROM v$session s;

Find your user and do the next query (with appropriate parameters):

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

Sometimes Oracle drop user takes long time to execute. In that case user might be connected to the database. Better you can kill user session and drop the user.

SQL> select 'alter system kill session ''' || sid || ',' || serial# || ''' immediate;' from v$session where username ='&USERNAME';

SQL> DROP USER barbie CASCADE;

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;
/

This can be as simple as:

SQL> ALTER SYSTEM ENABLE RESTRICTED SESSION;

SQL> DROP USER test CASCADE;

SQL> ALTER SYSTEM DISABLE RESTRICTED SESSION;

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;

:)