In Oracle, how can we ensure that users only have one session to log on?

In Oracle, how can I ensure that a user has only one session to log on to SQL> create profile one_session limit sessions_per_user 1; SQL> create User test identified by test; user created. www.2cto.com SQL> grant connect, resource to test; Grant succeeded. SQL> alter user test profile one_session; SQL> alter system set resource_limit = true; sqlplus test/testhost sqlplus test/test ERROR: ORA-02391: exceeded simultaneous SESSIONS_PER_USER limit. However, if it is RAC, you can log on to another instance.