Message Service 
Definition
The Message Service is a separate program used for communication between the J2EE server nodes and the J2EE dispatcher.
The Message Service is aware of all the active J2EE Instances.
Use
The Message Service is responsible for the following tasks in the J2EE cluster:
· Notification of events that arise in the cluster, for example, if a cluster node gets lost (through failure or shut-down of the instance), or when a service is started or stopped.
· Communication between different services
· Forwarding of messages and requests to all participants (broadcast)
· Prepare logon information for the SAP Web Dispatcher (see Load Balancing Between Many J2EE Instances)
· Support for Message Server failover
· Guaranteed message transmission
· Exchange of cache information in the cluster
Motivation
By using the Message Service you can avoid performance problems that occur if all the cluster elements are connected with each other and exchange data with each other. With large clusters especially this will result in considerable performance problems.
The same technology is used as with the SAP Message Server for the earlier SAP Web AS versions without Java.
See also:
Integration
The Message Service is addressed through the Cluster Manager of one of the processes in the J2EE cluster (dispatcher or server processes), as shown in the graphic below.
The settings and the status of the Message Service are made accessible to the administrator via the message Info Service in Visual Administrator. This is described in the administration manual under Message Info Service.
See also: