How to arrange centralized storage of OpenVPN certificates?

Question

openvpn

I am studying the issue of vpn-services (openvpn).
I can not understand yet how to store certificates centrally.
How can openvpn servers take certificates from one place and at the same time control that there are no connections to different servers with the same certificate at the same time?
Do you need a radius server for this? You can simply scatter certificates across servers, but then you won't be able to control duplicated connections.
Interested in a solution, information on this issue. Debian is used as the platform

Answer 1

1. a script that, while connecting a certificate to one of the servers on the others, will make it inactive. Upon completion, return the status.
2.