How to Disable Multiple Logins on SAP

To disable multiple user logins within the same client implement this parameter in the instance profile:
login/disable_multi_gui_login = 1

If you do not use this parameter in your system, users have the ability to ignore the warning window at the time they try to login to the same client. Activating this parameter in your system will make you look good if you get audited.
In case you’re wondering how to allow multiple logins for certain key users you can implement parameter login/multi_login_users. You can list the user IDs that should be ignored if the parameter above is active in your system.