Hi Mohanad,
Would a Data Partition Constraint work in Service Point? Perhaps an Update constraint set against (paraphrased) "category is not populated." An "Update" constraint prevents the save of information unless the statement is true.
Having said that, one of the design aims of the Service Point is that it should not get in the way of end users logging a ticket, even if they don't know or care what Request Area it is. The robot voice with dinky background piano music goes over that concept at 20 - 45 seconds in the introduction video here:
https://docops.ca.com/ca-service-management/17-2/en/using/service-pointSo perhaps another way to do it is not to touch anything to restrict the choice, but to automatically attach an Event to all tickets that would fire a Notification if there is no Request Area. Or for there to be a Stored Query that checks for these. Basically any monitoring along the lines of picking up empty Request Area tickets.
Thanks, Kyle_R.