WebSphere Application Server V7.0: Concepts ... - IBM Redbooks

While WebSphere Application Server profiles on z/OS are built using multiple
building blocks, it is still a single instance of an application server from an
application developer, system administrator, or user perspective. This means that
nearly all WebSphere variables can be defined against a server, and are not
defined against the servant and control region adjuncts. However some of the
settings, like heap sizes have to be done for each of the components.
All the possible profiles that can be instantiated, are built using the different
regions:
► Application server
► Deployment manager
► Job manager
► Administrative agent
Control region
The control region is the face of the application server to the outside world. It is
the only component that is reachable from the outside world using standard
protocols and port communication. For communication with the servant regions,
where the application is executed, the control region is the endpoint for TCP
transportation and switches to WLM queues.
Keep the following points in mind about control regions:
► An application server can only have one control region.
► The control region contains a JVM.
► The control region will be start- and endpoint for communication.
Servant region
The servant region is the component of an application server on z/OS where the
actual application is run and transactions are processed. The EJB and Web
container are included here.
As seen in Figure 14-2 on page 423, it is possible to have multiple servant
regions per application server. (But only one for the other profile types.) This
concept is called a multi-servant region or internal cluster. Through the usage of
this technique, it is possible to actually benefit from cluster benefits without the
overhead of a real cluster. For continuous availability and scalability, it is
suggested to build a WebSphere Application Server cluster that integrates these
mini clusters. While creating a normal cluster you can still use multiple servant
regions for each cluster member.
424 WebSphere Application Server V7.0: Concepts, Planning, and Design