Using the following profile options you can specify limits on user sessions.

ICX:Session Timeout
Use this profile option to enforce an inactivity time-out. If a user performs no Oracle Applications operation for a time period longer than the time-out value (specified in minutes), the user's session is disabled. The user is provided an opportunity to re-authenticate and re-enable a timed-out session. If re-authentication is successful, the session is re-enabled and no work is lost. Otherwise, Oracle Applications exits without saving pending work.

If this profile option to 0 or NULL, then user sessions will never time out due to inactivity.

ICX: Limit time
Use this profile option to specify the absolute maximum length of time (in hours) of any user session, active or inactive.