If you want some chance at controlling your job, make yourself vital but containing critical knowledge only to yourself. Everything is a process that requires steps, so take control of certain steps so that only you can do it! Important documents? Save them on your computer and not on the shared drive. Program access? Keep them to yourself. We all know how great our IT is.
If they let you go, get the satisfaction of knowing it’s going to implode or be one hell of a struggle without you. Find a way to cripple your department!