SQL> create profile one_session limit sessions_per_user 1 ;
Profile created.
SQL> alter user scott profile one_session;
User altered.
SQL> alter system set resource_limit=true;
System altered.
SQL> connect scott/tiger
Connected.
SQL> host sqlplus scott/tiger
SQL*Plus: Release 10.2.0.1.0 - Production on Sat Jul 5 15:02:21 2008
Copyright (c) 1982, 2005, Oracle. All rights reserved.
ERROR:
ORA-02391: exceeded simultaneous SESSIONS_PER_USER limit
Enter user-name:
