Introduction to WebSphere Application Server for z/OS

WebSphere® Application Server is a comprehensive, sophisticated, Java™ 2 Enterprise Edition (J2EE) and Web services technology-based application system.

WebSphere Application Server on z/OS® is the J2EE implementation conforming to the current Software Development Kit (SDK) specification supporting applications at an API level. As mentioned, it is a Java Application deployment and run-time environment built on open standards-based technology supporting all major functions such as servlets, Java server pages (JSPs), and Enterprise Java Beans (EJBs) including the latest technology integration of services and interfaces.

The application server runtime is highly integrated with all inherent features and services offered on z/OS. The application server can interact with all major subsystems on the operating system including DB2®, CICS®, and IMS™. It has extensive attributes for security, performance, scalability and recovery. The application server also uses sophisticated administration and tooling functions, thus providing seamless integration into any data center or server environment.

WebSphere Application Server is an e-business application deployment environment. It is built on open standards-based technology such as CORBA, HTML, HTTP, IIOP, and J2EE-compliant Java technology standards for servlets, Java Server Pages (JSP) technology, and Enterprise Java Beans (EJB), and it supports all Java APIs needed for J2EE compliance.

The Controller Address Space will automatically start a servant region as work arrives. As shown in Figure 1, an application server instance is composed of a controller region (CR) and one or more servant regions (SRs).

Figure 1. An application server instance

The application server on z/OS supports two types of configurations: Base and Network Deployment. Each configuration uses essentially the same architectural hierarchy, comprised of servers, nodes and cells. However, cells and nodes play an important role only in the Network Deployment configuration.

Servers

A server is the primary runtime component; this is where your application actually executes. The server provides containers and services that specialize in enabling the execution of specific Java application components. Each application server runs in its own Java Virtual Machine (JVM).

Depending on the configuration, servers might work separately or in combination, as follows:

In a Base configuration, each application server functions as a separate entity. There is no workload distribution or common administration among the application servers.
In a Network Deployment configuration, multiple application servers are maintained from a central administration point.

In addition, you can cluster application servers for workload distribution.

Note: A special type of application server called a JMS Server is not covered in this material.

Nodes (and node agents)

A node is a logical grouping of WebSphere-managed server processes that share common configuration and operational control. A node is generally associated with one physical installation of the application server.

As you move up to the more advanced application server configurations, the concepts of configuring multiple nodes from one common administration server and workload distribution among nodes are introduced. In these centralized management configurations, each node has a node agent that works with a Deployment Manager to manage administration processes.

Cells

A cell is a grouping of nodes into a single administrative domain. In the Base configuration, a cell contains one node. That node may have multiple servers, but the configuration files for each server are stored and maintained individually (XML-based).

With the Network Deployment configuration, a cell can consist of multiple nodes, all administered from a single point. The configuration and application files for all nodes in the cell are centralized into a cell master configuration repository. This centralized repository is managed by the Deployment manager process and synchronized out to local copies held on each of the nodes.

In the address spaces used for the application server, there is a concept of containers, which provide runtime separation between the various elements that execute. A single container, known as an EJB container, is used to run Enterprise Java Beans. Another container, known as the Web container, is used to execute Web-related elements such as HTML, GIF files, servlets, and Java server pages (JSPs). Together, they make up the application server runtime within the JVM.