Central Services 
Definition
The Central Services run on one physical server and are one J2EE instance.
They comprise the Message Service and the Enqueue Service.
Use
The Central Services form the basis of communication and synchronization for the J2EE cluster.
The Message Service keeps a list of J2EE dispatchers and J2EE server processes of the cluster. It represents the infrastructure for data exchange (small datasets only) between the participating nodes. The Message Service also supplies information to the SAP Web Dispatcher about Load Balancing Between Many J2EE Instances.
The Enqueue Service manages logical database locks, which are set by the executed application program in a J2EE server process. The Enqueue Service also synchronizes data across the cluster.
The section Deployment of a New Application describes how the central components handle the deployment of a new application.
Integration
Central Services are always required when a J2EE cluster is installed. They are started on a server with their own system number and the system ID (SID) of the whole system.
When Central Services are running, further J2EE instances are started with the program JControl (see J2EE Startup and Control Framework).
See also:
Administration of Central Services