ORA-00604/ORA-01422/ORA-06512 Error on trigger

Question

Hi,
I have an database which is of version 10.2.0.3.0 on Enterprise Edition.
I want to restrict a user from usage of an schema . Therefore i have written a trigger but i have encountered with another errors:
ORA-00604: error occurred at recursive SQL level 1
ORA-01422: exact fetch returns more than requested number of rows
ORA-06512: at line 5
Trigger Being::
SQL> create or replace trigger session_access
2 after logon on database
3 declare
4 v_username varchar2(30);
5 v_osuser varchar2(30);
6 begin
7 select username,osuser into v_username,v_osuser from v$session;
8 if v_username = 'SUSANJO' and v_osuser= 'ORACLE' then
9 raise_application_error (-20001,'Access restricted for this USER');
10 end if;
11 end;
12 /
Trigger created.
SQL> show errors;
No errors.
SQL> connect susanjo
Enter password:
ERROR:
ORA-00604: error occurred at recursive SQL level 1
ORA-01422: exact fetch returns more than requested number of rows
ORA-06512: at line 5
Warning: You are no longer connected to ORACLE.
i have run out of ideas of whats to be done onto the trigger now.
Regards.
Susan John

Answer 1

Um , i have implemented the following pl/sql. It seem to kick the person out BUT (now this is a big BUT) within the grid control it mentions :
Details          Failed to connect to database instance: ORA-00604: error occurred at recursive SQL level 1.
create or replace trigger session_access
DECLARE
v_username sys.v_$session.username%type;
v_osuser sys.v_$session.osuser%type;
BEGIN
select s.username ,s.osuser into v_username,v_osuser
from v$session s where s.username='SUSANJO' and s.osuser='oracle';
IF (v_username ='SUSANJO' AND V_OSUSER='oracle' )
THEN
RAISE_APPLICATION_ERROR(-20001, 'You are not allowed to login using the program');
END IF;
END session_access;
Output :
SQL*Plus: Release 10.2.0.3.0 - Production on Mon Mar 23 12:36:43 2009
Copyright (c) 1982, 2006, Oracle. All Rights Reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - Production
With the Partitioning and Data Mining options
SQL> connect susanjo
Enter password:
ERROR:
ORA-00604: error occurred at recursive SQL level 1
ORA-20001: You are not allowed to login using the program
ORA-06512: at line 10
Warning: You are no longer connected to ORACLE.
SQL>
I did conduct a research which was not all that helpful too. So i am back to square one again.
regards
Susan John