Cluster Administration

An SAP J2EE Engine 6.20 cluster consists of two types of nodes: server nodes and dispatcher nodes. The main function of dispatcher nodes is to reroute the requests coming from the clients to the server nodes. The server nodes process these requests and return the results to the dispatchers, which then send them back to the clients.

There are two possible cluster scenarios: single dispatcher with n servers, or m dispatchers with n servers. For more information on the advantages of using these options, refer to Planning the Architecture of a Cluster section.

General Requirements

There are a number of requirements that must be met to configure an SAP J2EE Engine 6.20 cluster.

There must be at least one dispatcher node; otherwise, no cluster can exist. The order in which the server nodes and the dispatcher node are started is not important; however, several server nodes cannot communicate with each other without the presence of a dispatcher.
All machines on which the dispatcher and server nodes are started must be on the same Local Area Network (LAN). The IP addresses of the hosts can be either static or dynamic.
All identical services on SAP J2EE Engine 6.20 nodes must be of the same version.
Typically, all identical services on the nodes in the cluster must be configured the same in relation to external resources.

Cluster Management with the Visual Administrator Tool

The Visual Administrator tool enables you to manage the different nodes in an SAP J2EE Engine 6.20 cluster. With this tool, the system administrator can manage cluster nodes and configure the modules running on them.

The tool provides the following modes of viewing the cluster nodes, and the modules running on them:

Tab View – three tabs are displayed in the left-hand pane of Visual Administrator. “Cluster” tab displays all running server and dispatcher nodes in the cluster. It provides information about the port, host, ID, type, and name of each node. “Managers” displays a list of all managers running in the cluster. “Services” displays a list of all services running in the cluster.
Cluster View – provides a tree view in which the main elements are the cluster nodes. The managers and services running on each cluster node can be displayed by expanding the tree.
Element View – displays a tree of all managers and services running in the cluster. When expanded, the tree also shows the nodes on which each module runs.

You can modify the administrable properties of the modules in each of the options for cluster viewing.

Note: For detailed information about SAP J2EE Engine 6.20 services and managers, refer to the Services Administration Reference and Managers Administration Reference sections in this document.

Cluster Management with the Console Administrator Tool

The SAP J2EE Engine 6.20 Console Administrator tool enables you to administer cluster nodes. Unlike Visual Administrator, it is not a GUI and the administration is done using Shell language commands. Commands can be input in the node prompt, or can be used for remote administration using a telnet client.

When using a telnet client, the system administrator must first run a single dispatcher and a single server. The administrator can then connect to the cluster (that is, to the dispatcher node) and to configure all other nodes in the cluster remotely. The Console Administrator commands are divided into groups, containing commands with different functions. Two of them – System Commands and Admin Commands – refer to SAP J2EE Engine 6.20 cluster administration.

Note: For detailed information about the Shell Language commands, refer to the Shell Commands Reference section in this document.