Special Edition Using SAP R/3, Third Edition

More documents

Recommendations

Info

Special Edition Using SAP R/3, Third Edition - CH 3 - Exploring R/3 Architecture Page 8 of 26 The most versatile configuration employs three levels of client/server distributed processing. In the core of the system is a high-speed network of R/3 database servers. The R/3 applications are networked around the database cluster and have independent access to it. The R/3 applications are fully integrated with each other. User access to any of the applications--and hence to any of the database servers--is mediated by an outer network of presentation servers that form the R/3 front-end systems, where they can be integrated with PC tools and subsystems. Figure 3.1 shows a triple-level client/server configuration. There is not a strict interpretation of level in this context, which could be referred to as multilevel client/server configuration. FIGURE 3.1 Triple client/server configuration. Even Loads Any user can be in touch with several application servers at the same time. In some areas, you might need to balance the load by installing specialized application servers. The following areas, in particular, are often served by systems optimized for their differing requirements: SD-Sales and Distribution FI-Financial Accounting HR-Human Resources Management Front-end and back-end computer systems are subject to different cost structures. The client/server architecture allows an economical deployment of computing resources by separating the three server levels. The advantage is experienced by the user in the form of generous computing resources for the display and prompting services that make the work easier and more effective. This can be seen in contrast to older systems, which had to compromise between the costs of presentation support systems and the cost of providing adequate central system resources. From the corporate point of view, the economy of providing specialized database servers allows a generous allocation of storage and processing resources to maintain extensive reference data and full historical information down to the business transaction detail level. Heterogeneous Platforms The SAP system has been designed to cope with change, including change in the hardware and operating systems. Therefore, the new SAP implementation must expect to integrate with the legacy of database and presentation platforms and operating systems that have been serving the company prior to the business process reengineering. For example, an R/3 installation can consist of the following assembly of heterogeneous platforms, in any combination: file://J:\prodinfo\MEMBERS\MA\ir057.html 3/23/01
Special Edition Using SAP R/3, Third Edition - CH 3 - Exploring R/3 Architecture Page 9 of 26 Presentation by Windows 3.1, UNIX, Windows NT, OS/2, Windows 95 Application by Windows NT, UNIX, Open VMS, MPE/iX Database by Windows NT, UNIX, Open VMS, MPE/iX, AS/400/DB2 Client/Server Communications The architecture of R/3 allows various protocols for communication between the elements of the configuration. TCP/IP and Open Systems Interconnect (OSI) are examples. The standard network protocol for open systems has become TCP/IP. It is supported by all operating systems relevant to R/3 systems. Transfer Protocols In accord with the SAP philosophy of choosing the most appropriate method for the task, different protocols have been adopted for each type of communication between the components of a multitiered client/server system: TCP/IP is used for handling communications within the client/server configurations of the R/3 system. The IBM network protocol LU6.2 is used for communication between the R/3 system and the mainframe host. Whatever transfer protocol is used, the interchange at the user interface is under the Systems, Applications, Products (SAP) presentation protocol. Data is transferred between an application and a database server using SQL, the fourthgeneration language for manipulating data defined by American National Standards Institute (ANSI). Data Transfer by WAN and LAN Linkage The SAP presentation protocol is optimized for linking presentation servers directly to the R/3 system and via wide-area networks (WANs). When a large volume of data has to be transferred, a local area network (LAN) is needed--for example, between database servers and applications. Program-to-Program Communications Basic services for program-to-program communications at the ABAP/4 programming level are implemented by using functions from the Common Programming Interface-Communication (CPI-C) standard. The start set of CPI-C has been integrated into the ABAP/4 language. When one program has to communicate with another program, an internal gateway is used to convert the CPI-C commands to the protocol used for external transfer, such as TCP/IP or LU6.2, according file://J:\prodinfo\MEMBERS\MA\ir057.html 3/23/01
Page 1 and 2: Special Edition Using SAP R/3, Thir
Page 7: Special Edition Using SAP R/3, Thir

Special Edition Using SAP R/3, Third Edition

Create successful ePaper yourself

Delete template?

Save as template?