The following diagrams illustrate the primary-elect feature. This feature is most useful in the case of the network disruption. It ensures application availability on both sites, even though the network is down.

In this example, the Primary site (seattle) is replicating data to the Secondary host (london) when a network disruption occurs. london has been identified as the Secondary for takeover.

After the takeover, london becomes the new Primary. The applications come online on london.

Because this event is a network disruption and not a site failure, the original Primary site, seattle, is still active. In the primary-elect feature, the applications on the original Primary site are not taken offline. Instead, application data is now being written to both sites, seattle and london.

When the network connection is restored, you can elect which of the two sites continues as the Primary. In this example the elected Primary is london and the elected Secondary is seattle.

Any data that was written to the elected Secondary (seattle) during the network disruption is lost. Any data that was written to the elected Primary (london) is intact.