IBM Reliable Scalable Cluster Technology (RSCT) is a set of software components that together provide a comprehensive clustering environment for AIX, Linux, Solaris, and Windows operating systems.
RSCT is the infrastructure used by a variety of IBM products to provide clusters with improved system availability, scalability, and ease of use.
The set of nodes that is configured for high availability is called an RSCT peer domain of your cluster.
A peer domain is a set of nodes that have a consistent knowledge of the existence of each other and of the resources shared among them.
In order to understand how the various RSCT components are used in a cluster, be aware that nodes of a cluster can be configured for manageability, high availability or both.