Load Balancing of Java Applications 
The purpose of load balancing is to distribute inbound requests optimally to the available resources.
Technical System Landscape
The SAP NetWeaver AS provides load balancing at various levels.
These are shown as (1) and (2) in the figure below.
Load balancing between many SAP NetWeaver AS instances (1)
You can start a system with many Java dispatchers, for which the SAP Web Dispatcher or a different load balancer is already activated as a Web switch. For more information, see Load Balancing Between Many Java Instances.
Load balancing within the SAP NetWeaver AS instance (2)
In the Java Instance the Java Dispatcher distributes the inbound requests to the Server Processes to which it is connected. The Java dispatcher runs the load balancing when the first session request arrives. The dispatcher ensures that subsequent requests get to the server process that is processing this session.
For more information, see:
Load Balancing by the Java Dispatcher