To configure BlackBerry® Collaboration Service high availability in a large-scale environment, you can configure each BlackBerry Collaboration Service instance to support up to four BlackBerry® Enterprise Server instances. For example, in the following diagram, failover pairs 1 and 2 of the BlackBerry Enterprise Server assigned the active connection to the same BlackBerry Collaboration Service instance. In failover pair 3, the primary BlackBerry Enterprise Server assigned the active connection to a different BlackBerry Collaboration Service instance.