A domain contains a group of GlassFish Server instances that are administered together. Each domain has a domain administration server (DAS) that hosts administrative applications. These concepts are explained in more detail in the following sections:
A GlassFish Server instance is a single Virtual Machine for the Java platform (Java Virtual Machine or JVM machine) on a single node in which GlassFish Server is running. A node defines the host where the GlassFish Server instance resides. The JVM machine must be compatible with the Java Platform, Enterprise Edition (Java EE).
GlassFish Server instances form the basis of an application deployment.
Whenever a domain is created, GlassFish Server creates a default instance that is named server. If a single instance meets your requirements, you can use this instance for deploying applications without the need to administer GlassFish Server instances explicitly. You administer the default instance when you administer its domain.
If you require multiple instances, you must administer the instances explicitly. For more information, see Chapter 5, Administering GlassFish Server Instances, in Oracle GlassFish Server 3.1-3.1.1 High Availability Administration Guide.
For an instance, you can also create virtual servers. Virtual servers do not span instances. For many purposes, you can use virtual servers instead of multiple instances in operational deployments. Virtual servers enable you to offer, within a single instance, separate domain names, IP addresses, and some administration capabilities to organizations or individuals. To these users, a virtual server behaves like a dedicated web server, but without the hardware and basic web server maintenance.
For more information about virtual servers, see Administering Virtual Servers.
A domain is an administrative boundary that contains a group of GlassFish Server instances that are administered together. Each instance can belong to only one domain. A domain provides a preconfigured runtime for user applications. Each domain has its own configuration data, log files, and application deployment areas that are independent of other domains. If the configuration is changed for one domain, the configurations of other domains are not affected.
Domains enable different organizations and administrators to share securely a single GlassFish Server installation. Each organization or administrator can administer the instances in a single domain without affecting the instances in other domains.
At installation time, GlassFish Server creates a default domain that is named domain1. After installation, you can create additional domains as necessary.
When a domain is created, you are prompted for the administration user name and password. If you accept the default, the user admin is created without password. To reset the administration password, see To Change an Administration Password in Oracle GlassFish Server 3.1 Security Guide.
The domain administration server (DAS) is a specially designated GlassFish Server instance that hosts administrative applications. The DAS is similar to any other GlassFish Server instance, except that the DAS has additional administration capabilities. The DAS authenticates the administrator, accepts requests from administration tools, and communicates with other instances in the domain to carry out the requests from administration tools.
Each domain has its own DAS with a unique administration port number. The default administration port is 4848, but a different port can be specified when a domain is created.
The DAS has the master copy of the configuration data for all instances in a domain. If an instance is destroyed, for example, because a host failed, the instance can be re-created from the data in the DAS.
The DAS is the default GlassFish Server instance in a domain and is named server. If a single instance meets your requirements, you can use the DAS for deploying applications and for administering the domain.
The graphical Administration Console communicates with a specific DAS to administer the domain that is associated with the DAS. Each Administration Console session enables you to configure and manage only one domain. If you create multiple domains, you must start a separate Administration Console session to manage each domain.