After an unexpected failure, the original Primary host might become available and find that one of its Secondary hosts has been promoted to a Primary as a result of a takeover. A takeover happens when a Secondary of the original Primary takes over the Primary role because of an unexpected outage of the original Primary. The process of transferring the Primary role back to the original Primary is called failback.

The fast-failback synchronization method can be used when the Fast failback option is selected during Takeover.

If you are sure that the original Primary will not recover or if most of the data on the new Primary is going to change while the original Primary is unavailable, you must synchronize the Secondary completely. In this case, you must failback using automatic synchronization.

See Failing back to the original Primary using VVR VEA.