One system can be supported by more than one node, forming a cluster. A vertical cluster consists of two or more application server instances on a single server.
For example, two copies of IBM WebSphere Application Server, each running a copy of Pega 7 Platform, can be installed on a single IBM server. A single PegaRULES database supporting both installations can reside on this server on another server. Interactive users connect to one or the other node based on distinct TCP/IP ports.
Vertical clustering provides both throughput and uptime benefits:
You can use horizontal clustering in combination with vertical clustering.