The Application Server creates one application server instance, called server at the time of installation. You can delete the server instance and create a new instance with a different name if you prefer.
Each Application Server instance has its own J2EE configuration, J2EE resources, application deployment areas, and server configuration settings. Changes to one application server instance have no effect on other application server instances. You can have many application server instances within one administrative domain.
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” areas to experiment with while developing.
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 To configure the JVM general settings.
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.
An Application Server instance is not started automatically. Once you start an instance, the instance runs until you stop it. When you stop an application server instance, it 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.