System Availability of 800xA DCS System using AC800M Controllers
What is the system availability of 800xA DCS System using AC 800M DCS Controllers
That's about as accurate an answer that you can get unless you want to tells us how many controllers, how much I/O, types, types of field bus used, wiring, third party components etc, the location where you're going to install the product, your environment, your industry. etc.
Any number you get off the Internet is worthless. Any Guarantee of system availability is a job for the sales team proposing the actual system for your plant.