Server Instance - Sun Microsystems GlassFish Enterprise Server 2.1 Administration Manual

Enterprise Server Concepts

Server Instance

The server instance is a single Java EE compatible Java Virtual Machine hosting an Enterprise
Server on a single node. Each server instance has a unique name in the domain. A clustered
server instance is a member of a cluster and receives all of its applications, resources, and
configuration from its parent cluster; ensuring that all instances in the cluster are
homogeneous. An unclustered server instance does not belong to a cluster and as such has an
independent set of applications, resources, and configuration. The following figure shows an
application server instance in detail. The application server instance is a building block in the
clustering, load balancing, and session persistence features of the Enterprise Server.
Enterprise Server Instance
FIGURE 1–1
The Sun GlassFish Enterprise Server creates one application server instance, called server, at
the time of installation. For many users, one application server instance meets their needs.
However, depending upon your environment, you might want to create one or more additional
application server instances. For example, in a development environment you can use different
application server instances to test different Enterprise Server configurations, or to compare
and test different application deployments. Because you can easily add or delete an application
server instance, you can use them to create temporary sandbox area for experimentation
purposes.
In addition, for each application server instance, you can also create virtual servers. Within a
single installed application server instance you can offer companies or individuals domain
Chapter 1 • Enterprise Server Overview 29