When admin_b is trying to edit a record, which is already being edited by admin_a, then special message is shown to admin_b.
This message explains, that record is already being edited by admin_a and some data loss might occur if both admins will save that record.
This functionality is disabled by default and can be individually enabled by specifying "CheckSimulatniousEdit" setting in unit config.
I've recently tried to use it on In-Portal 5.2.0 and found that it's no longer working.
Ready for testing.