Product architecture

This topic introduces the parts of the WebSphere Application Server product. The following diagram shows a product installation.

Product architecture and programming model, at a glance

Product subsystems	WebSphere applications	WebSphere applications
Servers Application servers More server types Core groups Workload balancing Environment Virtual hosts Variable settings Shared libraries Replication domains System administration Administrative clients Configuration files Domains (cells, nodes) Performance Monitoring Tuning performance Troubleshooting Diagnostic tools Support and self-help

Servers

Application servers. An
application server is a Java virtual machine (JVM) running user applications. Application servers use Java technology to extend Web server capabilities to handle Web application requests. An application server makes it possible for a server to generate a dynamic, customized response to a client request. The WebSphere Application Server product provides application servers.

For more introduction, refer to Introduction: Application servers.

Generic servers. In distributed platforms, you can use the generic servers feature to create a generic server as an application server instance within the product administration, and associate it with a non-WebSphere server or process. The generic server can be associated with any server or process that is necessary to support the application server environment.

For more information, refer to Server collection.

JMS servers. The product supports
asynchronous messaging based on the Java Message Service (JMS) of a JMS provider that conforms to the supported JMS specification. On the single-server product, the JMS functions (of the JMS provider) for an application server are served by the JMS server within the application server.

In the Network Deployment product, the JMS functions (of JMS providers) within the administrative domain are served by one or more JMS servers.

For more information, refer to Using asynchronous messaging.

Web servers. In the WebSphere Application Server product, an application server works with a Web server to handle requests for Web applications. The application server and Web server communicate using an HTTP plug-in for the Web server.

For more information, refer to Communicating with Web servers.

Core groups and core group bridges. A core group is a statically defined component of the high availability manager. The high availability manager is a product function that monitors the application server
environment and provides peer-to-peer failover of application server components. A core group bridge is a configurable service for communication between core groups.

For more information, refer to Core groups.

Clusters. In the Network Deployment product, clusters and cluster members help you monitor application servers and manage the workloads of servers.

For more information, refer to Balancing workloads with clusters.

Environment settings

Cell-wide settings help handle requests among Web applications, Web containers, and application servers in a logical administrative domain called a cell.

Virtual hosts. A virtual host is a configuration enabling a single host machine to resemble multiple host machines. Resources that are associated with one virtual host cannot share data with resources associated with another virtual host, even if the virtual hosts share the same physical machine. Each virtual host has a logical name and a list of one or more DNS aliases by which it is known. A DNS alias is the TCP/IP host name and port number that are used to request the servlet, for example: hostname:80.

For more information, refer to Virtual hosts.

WebSphere variables. Variables are used to control settings and properties relating to the server environment. WebSphere variables are used to configure product path names such as JAVA_HOME, cell-wide customization values, and the WebSphere Application Server for z/OS location service.

For more information, refer to Variables.

Shared libraries. Shared libraries are files used by multiple applications. You can define a shared library at the cell, node, or server level. You can then associate the library to an application or server in order for the classes represented by the shared library to be loaded in either a server-wide or application-specific class loader.

For more information, refer to Shared library files.

Replication domains. Replication is a service that transfers data, objects, or events among application servers. Data replication service (DRS) is the internal WebSphere Application Server component that replicates data. Replication domains transfer data, objects, or events for session manager, dynamic cache, or stateful session beans among application servers in a cluster.

For more information, refer to Replication.

System administration

Administrative console. The administrative console is a graphical interface that provides many features to guide you through deployment and systems administration tasks. Use it to explore available management options.

For more introduction, refer to Introduction: Administrative console.

Scripting client (wsadmin). The WebSphere administrative (wsadmin) scripting program is a powerful, non-graphical command interpreter environment enabling you to run administrative operations in a scripting language. You can also submit scripting language programs to run. The wsadmin tool is intended for production environments and unattended operations.

For more introduction, refer to Introduction: Administrative scripting (wsadmin).

Administrative programs (Java Management Extensions). The product supports a Java programming interface for developing administrative programs. All of the administrative tools that are supplied with the product are written according to the API, which is based on the industry standard Java Management Extensions (JMX) specification.

For more introduction, refer to Introduction: Administrative programs.

Command line tools. Command-line tools are simple programs that you run from an
operating system command-line prompt to perform specific tasks, as opposed to general purpose administration. Using the tools, you can start and stop application servers, check server status, add or remove nodes, and complete similar tasks.

For more introduction, refer to Introduction: Administrative commands.

Configuration files. Product configuration data resides in XML files that are manipulated by the previously mentioned administrative clients.

For more introduction, refer to Introduction: Administrative configuration data.

Domains (cells, nodes). Servers, nodes and node agents, cells, and the deployment manager are fundamental concepts in the administrative universe of the product. It is also important to understand the various processes in the administrative topology and the operating environment in which they apply.

For more introduction, refer to Welcome to basic administrative architecture.

PerformanceMonitoring tools. Performance monitoring is an activity in which you collect and analyze data about the performance of your applications and their environments. Performance monitoring tools include :

• Performance Monitoring Infrastructure (PMI) for monitoring to understand overall system health. For more information, see Performance Monitoring Infrastructure (PMI).

• Request metrics for monitoring to understand resource usage. For more information, see Why use request metrics?.

• Tivoli Performance Viewer (TPV) for viewing the performance data that you collected. For more information, see Why use Tivoli Performance Viewer?.

Tuning tools. Tuning the product helps you obtain the best performance from your Web site. Tuning the product involves analyzing performance data and determining the optimal server configuration. This determination requires considerable knowledge about the various components in the application server and their performance characteristics. The performance advisors encapsulate this knowledge, analyze the performance data and provide configuration recommendations to improve the application server performance. Therefore, the performance
advisors provide a starting point to the application server tuning process and help you without requiring that you become an expert.

For more information, refer to Obtaining performance advice from the performance advisors.

Troubleshooting

Diagnostic tools. Diagnostic tools help you isolate the source of problems. Many diagnostic tools are available for this product.

For more information, refer to Working with troubleshooting tools.

Support and self-help IBM Support can assist in deciphering the output of diagnostic tools. Refer to the WebSphere Application Server Technical Support Web site for current information on known problems and their resolution. Documents at this site can save you time gathering information that is needed to resolve a problem.

For more information, refer to http://www.ibm.com/eserver/iseries/support/ or see your local IBM representative.

Related concepts