The documents referenced here describe a concept and sofware products
that support High Availability (HA). The software product discussed
here is from IBM and is called High Availability Clustered
Multi-Processing (HACMP).
High Availability refers to the attempt to minimize downtime to
business functions by eliminating single points of failure (SPOF's).
This requires duplicating systems, networks, storage, and sofware to
eliminate these SPOF's.