The Effect of Changes on User Master Records
Changes to user master records take effect when the user next logs on. If a user is logged on at the time when the system administrator implements the changes, these will only take effect when the user logs on to their next session.
You can also change a user’s authorizations by changing and then reactivating profiles and authorizations within the user master record. Changes to reactivated authorizations have immediate effect. Changes to profiles, on the other hand, only take effect at the user’s next logon.