Architecture of the SAP NetWeaver Application Server

Purpose

The SAP NetWeaver Application Server is the central foundation for the entire SAP software stack. It also provides a platform for other NetWeaver components (Portal, XI, and so on), as well as for ABAP and Java applications. The full Java EE standard is supported. The SAP NetWeaver Application Server is the further development of the SAP Web Application Server.

Design

The design of the SAP NetWeaver Application Server is aimed at providing an exceptionally high level of robustness and supportability for the applications running on it. The NetWeaver Application Server consists of the Application Server ABAP (AS ABAP) and the Application Server Java (AS JAVA).

AS ABAP

The AS ABAP provides the complete technology and infrastructure to run ABAP applications.

It also enables selected SAP Java applications to run in the same work process (VM Container).

More information:

ABAP Application Server

SAP Virtual Machine Container

AS Java

The Application Server Java provides a Java™ 2 Enterprise Edition (Java EE) 1.5 compliant environment for developing and running Java EE programs.

For more information, see:

Application Server Java

Architecture of a Web AS Java System (Java Cluster)

Web Server and Web Client

The SAP NW AS can function both as a Web server and as a Web client. In its Web server role, it can accept HTTP requests from any Web client (for example, a browser), process the requests, and send a response back to the client.

If you use the SAP NetWeaver Application Server as a client, you can create HTTP requests in an application program, and sends these requests to a Web server. The client then receives the responses and proceeds on the basis of the responses.

In both roles, the SAP Web Application Server can operate in stateful mode (context is kept open) or stateless mode (context is terminated every time).

More information:

Processing HTTP Requests in the Work Process

SAP NW AS as a Web Client

Technical Components

An SAP system consists of several application server instances, as well as one or more databases.

In addition to multiple dialog instances that execute user requests, there is a special instance that contains the message server and the enqueue server - the SCS (System Central Services) for the AS Java, the ASCS (ABAP System Central Services). It cannot process any dialog requests.

A dialog instance with AS ABAP and AS Java consists of the following components:

● The Internet Communication Manager (ICM) sets up the connection to the Internet. It can process both server and client Web requests. It supports HTTP, HTTPS und SMTP protocols for the AS ABAP. In AS Java the ICM supports the HTTP(S), P4, IIOP and Telnet protocols. The SAP NW AS can act as a Web server or a Web client.

● Central services (message server and enqueue server) are used for lock administration, message exchange, and load balancing in the SAP system.

● AS ABAP components (in the graphic on the left):

○ The dispatcher distributes the requests to the work processes. If all the processes are occupied the requests are stored in the dispatcher queue.

○ The work processes execute ABAP or Java programs.

○ The SAP Gateway provides the RFC interface between the SAP instances (within an SAP system and beyond system boundaries).

● AS Java components (in the graphic on the right):

○ The Server Processes execute Java requests.

○ The instance controller controls and monitors the life cycle of the AS Java instance.

More information:

Internet Communication Manager (ICM)

Work Process (BC-CST)

SAP Gateway

Java Cluster Architecture.

The graphic below shows the components of the SAP NetWeaver Application Server (in grey). To retain clarity a few communication channels are not included in the graphic.

Installation Options

There are the following installation options for the SAP NetWeaver AS:

● ABAP System (with integrated VM Container). In the graphic these are the components in the blue box on the left. With this installation you can run ABAP programs and selected SAP Java applications.

● Java System In the graphic these are the components in the green box on the right. With this installation you can run Java EE applications but not any ABAP programs.

● ABAP+Java System These are all the components in the graphic