If the Primary fails, update the Secondary from the bunker.

See Updating the Secondary from the bunker using VVR VEA.

After the Secondary is up-to-date, the Secondary can take over the role of the Primary.

See Taking over from an original Primary using VVR VEA.

When the Primary recovers, fail back to the original Primary.

See Failing back to the original Primary using VVR VEA.