SQL & PL/SQL

Hi Friends,

Could you tellme as to why the following trigger fired when I logong to a database (the user4s database).
This code should try to capture the logon entries in v$session view and then if there is any logon entry, then the the exception is raised.

-----------
create or replace trigger logcheck after logon on database
declare

cursor user_cur is select username, program from v$session
where to_char(logon_time, 'DD-MON-YY') = to_char(sysdate, 'DD-MON-YY');
begin
for user_rec in user_cur loop
begin
if user_rec.username='SAM' and upper(user_rec.program)='SQLPLUSW.EXE' then
insert into nc_login values (sysdate, user_rec.username, user_rec.program);
commit;
raise_application_error(-20201, 'No login allowed');
end if;
END;
end loop;
end;
----

1)Can you tellme what is wrong in this code and when I login to the database as SAM, this trigger is not fired!
2) I know that there may be other ways of doing the same task.. Please assume that the table is NC_LOGIN is existiing, used to store all those attempts to logon to the database.

I appreciate your early feed back on this!

Thanks in advance,
Sam