SQL & PL/SQL

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