The Java Instance Concept
SAP NetWeaver Application Server Java
takes the instance concept of SAP Basis, which combines multiple components
that are monitored, started, and stopped together into an administrative unit.
The following components are part of a
Java instance:
• The server processes provide
the infrastructure in which the Java™ EE 6 applications run.
• The Internet Communication
Manager distributes the client requests to the free server processes of the
instance.
An instance always runs on one
physical server, but there can be multiple instances on one server. Within an
SAP system, an instance is defined using the system ID (SID) of the SAP system
and the instance number. An SAP system consists of a database and one or more
instances. These instances can either be purely ABAP or Java instances, or
instances with ABAP and Java infrastructure, with the instances of a system
always having the same infrastructure (that is, there is no system that has
ABAP instances (without Java) and Java instances (without ABAP).
Communication and synchronization
within a Java cluster. Another special instance is the instance that is
installed first. It is often referred to as the Primary Application Server
Instance or PAS for short. Further instances for a system are
referred to as Additional Application Server Instances or AAS for
short. To ensure high-performance when processing Java requests, the SAP system
can be scaled using the number of server processes for each instance or using
the number of instances.
Note:
The terms central instance and dialog instance no longer apply as of 7.1 and
the terms PAS and AAS comes into the picture.
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