What is the Application Server?

The Application Server is a platform that supports services from Web publishing to enterprise-scale transaction processing, while enabling developers s to build applications based on JavaServer Pages (JSP), Java servlets, and Enterprise JavaBeans (EJB) technology.

The Application Server Platform Edition is free for development, production deployment, and redistribution. For more information on redistribution, please visit http://www.sun.com/software/products/appsrvr/appsrvr_oem.xml.

The Application Server Enterprise Edition provides advanced clustering and failover technologies. The Application Server infrastructure supports the deployment of many types of distributed applications and is an ideal foundation for building applications based on Service Oriented Architectures (SOA). SOA is a design methodology aimed at maximizing the reuse of application services. These features enable you to run scalable and highly available J2EE applications.

• Scalability - Scalability is achieved through clustering. A cluster is a group of application server instances that work together as one logical entity. Each Application Server instance in a cluster has the same configuration and the same applications deployed to it.

  Horizontal scaling is achieved by adding Application Server instances to a cluster, thereby increasing the capacity of the system. It is possible to add Application Server instances to a cluster without disrupting service. The HTTP, RMI/IIOP, and JMS load balancing systems distribute requests to healthy Application Server instances in the cluster.

• High Availability - Availability refers to the failover capability. If one server instance goes down, another server instance in a cluster takes over the sessions of the failed instance and continues to serve the clients in a seamless manner. Session information is stored in the high-availability database (HADB). HADB supports the persistence of HTTP sessions and stateful session beans.