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

Keep in mind the following information about servant regions:
► Each servant region contains its own, independent JVM.
► All servant regions are identical to each other.
► An application runs on all servant regions connected to an application server,
because it is deployed at server scope.
► An application must be WebSphere Application Server cluster-ready to use
the multi-servant concept.
► The number of servant regions is transparent to the user and the application.
► Servant regions can be started dynamically by the WLM component, if
response times of user transactions do not meet the defined goals. The
defined maximum is the limit.
► If a single servant fails, the others will still run, keeping the application alive.
Only the transactions of the crashed servant region will fail and deliver errors
to the user. The other servant regions will continue to work.
► Failed servant regions will be restarted automatically by the operating system
providing a miniature automation.
Control region adjunct
The control region adjunct is a specialized servant that interfaces with new
service integration buses to provide messaging services.
14.1.5 Runtime processes
Note: When determining the maximum number of servant regions, make
sure that the system has enough resources to use them all.
This section describes the runtime behavior of the WebSphere Application
Server for z/OS V7.0.
Overview
The non-z/OS platforms are built on a single process model. This means the
entire application server runs in one single Java Virtual Machine (JVM) process.
WebSphere Application Server for z/OS is built using a federation of JVM’s, each
executing in a different address space. Together, such a collection represents a
single server instance, as described in Figure 14-2 on page 423.
Chapter 14. WebSphere Application Server for z/OS 425