High Availability (HA) involves ensuring that the complete application can continue to function in the event of a disaster. These types of disasters can be local to the application or regional. Both scenarios must be taken into account. HA includes ensuring data integrity as well as making sure the application infrastructure is available to access the data as well.
There is a whitepaper that will begin to address these two areas – data replication and application infrastructure (specifically OpenEdge Application Servers).