Sun Java System Application Server 9.1 Administration Guide

Server Instance

The server instance is a single Java EE compatible Java Virtual Machine hosting an Application 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 Application Server.

Figure 1–2 Application Server Instance

Figure shows server instance features and how they communicate
with various clients, databases, and other servers and systems.

The Sun Java System Application 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 Application 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 names, IP Addresses, and some administration capabilities. For the users, it is almost as if they have their own web server, without the hardware and basic server maintenance. These virtual servers do not span application server instances. For more information about virtual servers, see Chapter 13, Configuring the HTTP Service.

In operational deployments, for many purposes you can use virtual servers instead of multiple application server instances. However, if virtual servers do not meet your needs, you can also use multiple application server instances. On stopping, application server instance stops accepting new connections, then waits for all outstanding connections to complete. If your machine crashes or is taken offline, the server quits and any requests it was servicing may be lost.

Defining Application Server Instances

Application server instances form the basis of an application deployment. Each instance belongs to a single domain and has its own directory structure, configuration, and deployed applications. Each server instance also includes the Java EE platform web and EJB containers. Every new server instance must contain a reference to a node agent name defining the machine on which the instance will reside.

Note –

You cannot create Application Server instances on a developer domain. A developer domain is always associated only with the default instance, server1. To create multiple instances, you need to create a domain with the cluster profile. For information on creating domains, see the manpage for the command create-domain or consult the Admin Console Online Help.

You can create three types of server instances:

Viewing General Server Information

From the General Tab you can perform the following tasks:

In addition, you can select the following tabs to perform these additional tasks:

Note –

The Start Instance option and tabs such as Rresources and Properties are not available if you are running Admin Console on a Developer Profile.