At the peak of the U.S. Navy Reserve's "RHS" project (Reserve HQ Support), we had licenses for the FE package for 350 users and because of internal batch processes that ran as a generic super-user, the ORACLE backend was in the 500-session range. It wasn't Windows/Access, though. With the memory we had on our Itanium servers, we could have managed about 1200-1500 users but there weren't that many personnel managers on our system and we bottle-necked the batch jobs so we only ran four or five at a time during daytime hours.