I have tried it. And what happens is the security warning pops up and says that type of file is not allowed. I work on a military base.
I worked for 28 1/2 years with the U.S. Navy, different department names, but always associated with the Navy Reserves, and split databases were NEVER an issue. We had an Access front-end with an SQL Server back-end (therefore certainly split) that ran a BUMED (medical) personnel management program for Navy officer medical school scholarships. I had a pure Access application with a simple two-way split that helped track and manage computer system compliance with mandated and optional security hardening activities. It only took me a couple of sessions with the IT head to calm him down and leave us alone.
1. Note the exact message that you get. If it is a "security center" message we can advise you how to shut that up. If the security warning pops up that says the file type or action is not allowed, note the reason it gives, by site policy or by a specific department, you may still have a way out.
2. Tell your supervisor or whoever wants that DB that in order to stabilize the database, you need to split it in a certain way that is standardized and performed by the Access database splitter built-in tool. (I.e. no special processing by a third-party product and no manual processing.)
3. Tell your supervisor that if you split it, you will be able to allow multiple simultaneous users fairly cleanly (with our help.)
4. Tell any of your IT people who object to this idea to make a list of questions and come back here with that list so that we can answer their objections. We will be able to describe how to manage permissions very precisely regarding who can and who can't use the DB, using methods that ARE approved by DOD rules.
5. IF the problem is that you are running on a machine with SECRET or higher clearance, you are going to be in a world of hurt anyway, as Access is not usually considered compliant with that level of security.
6. The REAL trick here is that you think (and probably are correct) that you don't have enough clout to make something good happen. But if the persons who want this can be enticed with potential improvements, THEY might have enough clout to help you politically while you continue with the technical and implementation issues. Don't go banging your head against a brick wall. Let someone else have that fun.