Two SEP servers in two sites

I've two SEP 12.1.6 servers in two sites. One of them manage 200 PCs + servers, while the other manages 150 PCs+servers.

They are physical servers running under Windows Server 2012 R2 and installed with embedded databases.

Juse name them server A and server B.

I'm being asked how if server A is down for a prolonged period, how can the PCs and servers managed by server A being managed by server B?

Thanks