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.
A base WebSphere Application Server (single server) installation includes only the Application Server process. A single server installation can host one or more sets of managed servers, known as nodes. A managed server is a single WebSphere Application Server JVM instance, running in its own process. A node cannot span multiple machines, but a machine can have multiple nodes, each with multiple managed servers. There is no node agent or network deployment manager involved in this configuration. No coordination between application server processes is supported in the single server environment. Administration is limited to a single process at a time.
A Network Deployment installation can support a network of computer systems that are configured to run collaborating instances of a single server installation. Each computer having a single server installation is known as a node. The Network Deployment product provides centralized administration and workload management for a set of nodes, known as a cell. A cell has a master administrative repository that stores all of the cell's configuration data.
One computer is designated as the central deployment manager machine. The central deployment manager program (dmgr) oversees the cell.
In the Network Deployment product, each node has a node agent that serves as an intermediary between the application servers on the node and the deployment manager that oversees the entire cell.
Administrative logic running in a node agent keeps the configuration data of a node synchronized with the configuration data of all nodes within a cell.
You establish a multiple machine environment (a cell) through a series of installation and configuration steps.