Sync connector between UCS

please correct me if i am wrong

I am trying to use UCS AD at two locations with gateway vpn connecting two sites. In order to increase speed and stability (or to have AD still working while VPN is down), I tried to set up 2 UCS servers, and one at each location. I am looking for solution to sync the user data and password between these two UCS servers. However, the current Active Directory Connection is designed to join the UCS to Microsoft AD.
(Active Directory Connection brings together the domain managed by Univention Corporate Server and an existing Active Directory.)
but does not connect two UCS. (I tried, using it to connect two UCS, but I got issue at the password sync.)

I think an app connecting (sync) two UCS will be very helpful.
Please correct me if there is such feature already or have better solution exist.

thanks a lot

Why dont you set up a DC Slave or DC Backup on the second site?
1.2.2. Domain concept