Central Services

Definition

The Central Services run on one physical machine and constitute a Java instance.

They comprise the Message Service and the Enqueue Servicesapurl_link_0001_0002_0007.

Use

The Central Services form the basis of communication and synchronization for the Java cluster.

The Message Service keeps a list of the dispatchers and server processes of the Java 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 Java Instances.

The Enqueue Service manages logical database locks, which are set by the executed application program in a 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

The Central Services are always required when a Java cluster is installed. The Central Services instance has its own system number.

When Central Services are running, further Java instances are started with the program JControl. For more information, see Java Startup and Control Framework.

See also:

Java Instance

Administration of Central Services