Before Release 5.1 SP1, if a disaster struck at the Primary site or a network disruption, the applications were taken offline on the original Primary and failed over to the Secondary.
When the original Primary returned or the network disruption was corrected, you had the following options:
Manually resynchronize the original Primary
Automatically resynchronize the original Primary
Beginning in Release 5.1 SP1, you have a third option. After the original Primary returns or the network disruption is corrected, you can specify which site is the Primary going forward. This feature is called the primary-elect feature, and it is enabled through the VCS Global Cluster Option. The key difference between the primary-elect feature and the other options is that if a network disruption occurs, applications continue to run on the Primary site and they are also failed over to the Secondary. This allows you to maintain application availability on both sites while the network is down.