Exploiting the SAP Netweaver Application Server Architecture
SAP systems are used for running business processes or business applications. These applications need to be implemented independent of the hardware environment used (operating system and database) to the greatest extent possible
SAP NetWeaver provides the following runtime environments:
- ABAP runtime environment (AS ABAP)
- Java runtime environment (AS Java)
ABAP Runtime Environment
ABAP is a programming language developed by SAP. Many business applications in the SAP system are written in ABAP. ABAP has been optimized for developing highly scalable business applications. Customers can use the ABAP Workbench for developing completely new applications or enhancing and modifying standard SAP applications. Applications are developed or enhanced using the infrastructure of AS ABAP. AS ABAP provides the runtime environmentfor programs written in ABAP.SAP provides a runtime environment for ABAP programs and Java programs.
Java Runtime Environment
AS Java is an application server, based on the Java 2 Enterprise Edition (J2EE) standard. Java is an object-oriented and a platform-independent programming language that has spread across many areas. The Java concept enables the development of a large range of applications from classical applications to applets used in websites to client/ server applications.As of SAP Web Application Server 6.20, SAP has provided a complete Java EE-compatible runtime infrastructure. Up to SAP NetWeaver AS Java 7.0, the infrastructure was compliant with J2EE 1.3.
AS Java 7.1x are EE 5-compliant, and as of AS Java 7.3x, they are EE6-compliant. The architecture of an application server in accordance with the Java EE specification is similar to the ABAP runtime environment used for SAP solutions. Both runtime environments are platform-independent, executed in a multi-level architecture, and have a separate presentation logic and business logic.
Using Java EE in SAP technology has the following advantages for SAP Netweaver Application Server:
- The open integration architecture SAP NetWeaver integrates perfectly into the openness of Java EE.
- Java EE is further proof of the strategy of platform-independence pursued by SAP.
- The Java EE Connector architecture allows standardized integration of external applications.
- Web Services technologies are supported directly by Java.
- The quickly-growing Java community provides simple access to experienced developers.
Client and Server – Terminology Definition
The concepts of client and server can be defined in the following ways:
- In the hardware-oriented view, the term server means the central server in a network that provides data, memory, and resources for workstations (clients).
- In the software-oriented view, client and server are both defined at the process level (service). The process requesting a service is the client, and the server is the process providing the service.
In the context of SAP systems, the terms "client" and "server" are used as defined in the software-oriented view.
Image provided by SAP
Client/Server Configuration for SAP Systems
The following processes are used for operating business application software:
- Presentation processes (for example, for displaying screens)
- Application processes (for example, for executing applications)
- Database processes (for example, for managing and organizing databases)
When you are installing and configuring an SAP system, you need to decide how you are going to distribute the required processes among the available hardware. SAP ECC (SAP Enterprise Core Component) is an example of business application software. The figure shows different types of configurations in relation to the number of hardware layers used.
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Single-Tier, Two-Tier, and Three-Tier Configurations
Single-Tier Configuration
Single-tier configurations are used for tests and demonstrations (for example, an SAP system on a laptop). If many users want to work on a system in single-tier configuration, then the extra hardware cost for each additional user becomes greater than the costs of implementing additional hardware levels (for example, moving the presentation processes to other hosts).
Two-Tier Configuration
An alternative two-tier configuration is to install powerful desktop systems and use them for presentation and application processes (two-tier client/server). This configuration is especially suitable for applications that have high processor demands (for example, for simulations or software developers). Such a configuration is implemented in the SAP environment only for testing purposes because it requires additional administration.
Three-Tier Configuration
If the number of users exceeds a certain upper limit, the central host, on which we run our application and database processes, will become a bottleneck. To prevent such a bottleneck, you can improve the performance of the SAP system by distributing the application-layer processes among several hosts.
The addition of a hardware layer specifically for application processes facilitates scalability. If the number of SAP users in a system increases over time, it negatively affects system performance. To improve system performance, another host can be added for application processes in most cases.
Instance
When you install an SAP system, you have the option of separating the processes at application level from the processes at database level. This means that the installation and operation of the database for an SAP system can be done on a separate physical computer, separated from the instances of the SAP system. There is exactly one database for each SAP system. The database has the same system ID (DB ID) as the SAP system.
The central instance of an SAP system offers services that no other instance of the system offers. For AS ABAP, the central instance provides the message server and the enqueue work process.
The central services instance provides central services of AS Java and the message and enqueue services. For AS ABAP, these services can also be moved to the ABAP central services instance for high-availability reasons. If the services are moved, the AS ABAP systems would no longer have a central instance.
All other instances of a system are typically called dialog instances.
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Central Instance
If the central instance and the database (and for AS Java, the central services instance also) are installed on the same computer, the computer is referred to as a central system.
SAP System
The SAP system is an installed software system that provides a defined set of functions that are part of an SAP solution. These functions are implemented in a set of software components. An SAP system is installed and configured as a unit. It consists of a database, one or more application server instances (ABAP and/or Java), central services (such as a message server and enqueue server), and optional components (such as TREX and liveCache). The system is identified by its SAP system ID, which consists of three letters or digits (for example PRD).