SAP R/3 System Architecture

SAP based the architecture of R/3 on a three-tier client/server model.

Presentation Server

Application Server

Database Server


Presentation Server

The presentation server is actually a program named sapgui.exe. It is usually installed on a user's workstation. To start it, the user double-clicks on an icon on the desktop or chooses a menu path. When started, the presentation server displays the R/3 menus within a window. This window is commonly known as the SAPGUI, or the user interface (or simply, the interface). The interface accepts input from the user in the form of keystrokes, mouse-clicks, and function keys, and sends these requests to the application server to be processed. The application server sends the results back to the SAPGUI which then formats the output for display to the user.
Application Server

An application server is a set of executables that collectively interpret the ABAP/4 programs and manage the input and output for them. When an application server is started, these executables all start at the same time. When an application server is stopped, they all shut down together. The number of processes that start up when you bring up the application server is defined in a single configuration file called the application server profile.

Each application server has a profile that specifies its characteristics when it starts up and while it is running. For example, an application sever profile specifies:

* Number of processes and their types
* Amount of memory each process may use
* Length of time a user is inactive before being automatically logged off

The application server exists to interpret ABAP/4 programs, and they only run there-the programs do not run on the presentation server. An ABAP/4 program can start an executable on the presentation server, but an ABAP/4 program cannot execute there.

If your ABAP/4 program requests information from the database, the application server will format the request and send it to the database server.
Discovering the Database Server

The database server is a set of executables that accept database requests from the application server. These requests are passed on to the RDBMS (Relation Database Management System). The RDBMS sends the data back to the database server, which then passes the information back to the application server. The application server in turn passes that information to your ABAP/4 program.

There is usually a separate computer dedicated to house the database server, and the RDBMS may run on that computer also, or may be installed on its own computer.
Configuring the Servers

In a three-tier client/server configuration, the presentation servers, applications servers, and database server all run on separate machines. This is the most common configuration for large systems, and is common in production.

In the distribution presentation configuration, the application and database servers are combined on one computer and the presentation servers run separately. This is used for smaller systems, and is often seen on a development system.

In the two-tier client/server configuration, the presentation and application servers are combined and the database server is separate. This configuration is used in conjunction with other application servers. It is used for a batch server when the batch is segregated from the online servers. A SAPGUI is installed on it to provide local control.

When all servers are combined onto a single machine, you have a central configuration. This is rarely seen because it describes a standalone R/3 system with only a single user.
Defining an R/3 System

The simplest definition of an R/3 system is "one database." In one R/3 system, there is only one database. To expand the definition, R/3 is considered to be all of the components attached to that one database. One R/3 system is composed of one database server accessing a single database, one or more application servers, and one or more presentation servers. By definition, it is all of the components attached to one database. If you have one database, you have one system. If you have one system, you have one database. During an implementation, there is usually one system (or one database) assigned to development, one or more systems designated for testing, and one assigned to production.

The term R/3 system landscape denotes a description of the number of systems within an SAP installation and how they are designated, such as development, test, or production.
Defining an R/3 Instance

When you hear someone say the word instance, most of the time, that person will be referring to an application server. The term instance is synonymous with application server.

The term central instance refers to the database server. If an application server and database server both reside on the same machine, the term central instance refers to the computer on which both reside.

In the most general terms, an instance is a server. It is a set of R/3 processes providing services to the R/3 system.
Application Server Architecture

All requests that come in from presentation servers are directed first to the dispatcher. The dispatcher writes them first to the dispatcher queue. The dispatcher pulls the requests from the queue on a first-in, first-out basis. Each request is then allocated to the first available work process. A work process handles one request at a time.

To perform any processing for a user's request, a work process needs to address two special memory areas: the user context and the program roll area. The user context is a memory area that contains information about the user, and the roll area is a memory area that contains information about the programs execution.
Understanding a User Context

A user context is memory that is allocated to contain the characteristics of a user that is logged on the R/3 system. It holds information needed by R/3 about the user, such as:

* The user's current settings
* The user's authorizations
* The names of the programs the user is currently running

When a user logs on, a user context is allocated for that logon. When they log off, it is freed. It is used during program processing, and its importance is described further in the following sections.
Understanding a Roll Area

A roll area is memory that is allocated by a work process for an instance of a program. It holds information needed by R/3 about the program's execution, such as:

* The values of the variables
* The dynamic memory allocations
* The current program pointer

Each time a user starts a program, a roll area is created for that instance of the program. If two users run the same program at the same time, two roll areas will exist-one for each user. The roll area is freed when the program ends.

What is SAP ALE?

ALE is SAP proprietary technology that enables data communications between two or more SAP R/3 systems and/or R/3 and external systems. When a new enterprise resource planning (ERP) solution such as R/3 is implemented, companies have to interface the ERP system with legacy systems or other ERP systems. ALE provides intelligent mechanisms whereby clients can achieve integration as well as distribution of applications and data. ALE technology facilitates rapid application prototyping and application interface development, thus reducing implementation time. The ALE components are inherently integrated with SAP applications and are robust, leading to a highly reliable system. ALE comes with application distribution/integration scenarios as well as a set of tools, programs, data definitions, and methodologies that you can easily configure to get an interface up and running.

The message-based architecture of ALE comprises three layers:

Application layer. This layer provides ALE with an interface to R/3 to originate or receive messages containing data to or from external (or other R/3) systems.

Distribution layer. The distribution layer filters and converts messages containing data based on predefined or custom-defined rule sets. These conversions may occur to ensure compatibility between different releases of R/3 and R/2.

Communications layer. ALE communications are carried out both synchronously and asynchronously. Synchronous message transmissions are typically used for the direct reading of control data, while asynchronous message transmissions are used for transmitting or receiving application data. It is also possible to achieve a pseudo-real-time exchange of application data using transactional Remote Function Calls (tRFC), which I’ll detail later in this article series.

ALE scenarios fall into three categories: master data, transactional data, and control data distribution. Although the underlying principles are the same for the different categories, there are differences in their functions and configurations. SAP delivers over 200 ALE scenarios; and by extension there are approximately 200 application areas that can leverage ALE technology for data distribution or communication. A subset of these scenarios is supported by R/3 for Electronic Data Interchange (EDI).

There are several advantages to using ALE technology:

• SAP ensures release independence.
• Robust mechanisms capture changes to master data or transactional data.
• ALE offers better inbound interface performance compared to traditional techniques such as Batch Data Communications (BDC) or Call Transactions. ALE does not use screen-based batch input.
• ALE provides black-box technology, so the user is at a higher level.
• Most ALE interfaces can be prototyped in a couple of days, resulting in smaller implementation timelines.
• There is little or no ABAP program development. In most cases, the SAP-delivered ALE functionality meets the requirements.
• ALE offers a systematic and organized approach to custom enhancements and extensions.
• An ALE interface is easy to maintain due to the structured approach and minimal number of development objects.
• ALE is the strategic architecture for R/3 “loose coupling” with legacy and third-party applications and is a Business Framework key element. It provides a message-based architecture for asynchronous integration of Business Framework components, including Business Components, Business Objects, and BAPIs.

SAP official Certification Levels

* Associate certification – This certification covers the fundamental knowledge requirements for a SAP consultant, or project team member ensuring the successful acquisition of broad SAP solution knowledge and skills. With associate-level certification, you can:
o Gain an externally-recognized mark of excellence that clients seek
o Differentiate yourself in a crowded marketplace
o Execute your tasks with confidence and skill
* Professional certification – This advanced certification requires proven project experience, business process knowledge, and a more detailed understanding of SAP solutions. With professional-level certification, you can:
o Demonstrate both your experience and your expertise through a rigorous testing process
o Promote a more globally applicable accreditation with higher billable rates
o Lead as well as execute tasks and engagements
* Master certification (in development) – This certification will involve demonstrating an expert-level understanding of a specific area of SAP software and the ability to drive innovation and solution optimization through in-depth knowledge and vision. Certification at this level requires broad project experience, comprehensive SAP product knowledge, and the ability to create a future IT vision within complex project environments. With master-level certification, you can:
o Secure your place in an exclusive community of visionary experts
o Pass a peer-reviewed, comprehensive admissions process
o Define and guide long term strategy
o Participate in master-level briefings, colloquiums, and industry events

Certification Focus Areas

* Application certification – This certification is available for specific SAP solutions. You can take the certification exam after completing the appropriate solution academy course and case study, or the equivalent SAP standard curriculum. If you already have significant experience implementing an SAP solution, you can take the exam without attending the course but participation is highly recommended.
* Technology certification – If you complete the solution academy or SAP training classes, you can take the technology exam to become certified. If you already have significant experience with SAP technology, you can take the exam without attending the course but participation is highly recommended.
* Development certification – This certification is available for individuals who are developing applications for SAP solutions. If you already have significant experience with SAP development, you can take the exam without attending the course but participation is highly recommended.

What is SAP (Systems, Applications and Products in Data Processing)

"SAP is one of the largest software company in the world. Its ranking is after Microsoft,IBM and Oracle in terms of market capitalization. SAP is the largest Enterprise Resource Planning (ERP) solution software provider.SAP's products focus on ERP ( enter prise resource planning ), which it helped to pioneer. The company's main product is SAP R/3;the "R" stands for real time data processing and the number 3 relates to a three-tier application architecture: database, application server and client SAPgui ( presentation layer ).Other major product offerings include Advanced Planner and Optimizer (APO),Business Information Warehouse(BW),Customer Relationship Management(CRM),Supplier Relationship Management(SRM), Human Resource Management Systems(HRMS),Product Lifecycle Management(PLM), Exchange Infrastructure(XI) and Knowledge Warehouse(KW).Reportedly, there are over 91,500 SAP installations at more than 28,000 companies as per the statistics of 3 years before. SAP products are used by over 12 million people in more than 120 countries." In this website we trying to collect , arrange different SAP materials for professionals seeking for references. Mainly we are trying to collect ABAP tutorials, BAPI, LSMW, IDOC, ALE, ABAY syntx, NetWeaver, SAP HR, SAP MM, SAP SD, FICO, PP, PM like functional modules, interview questions and answers. latest sap jobs informations also available in the site. users can also contribute their materials or articles for helping other professionals.Its just an online help for the SAP professionals searching for materials, tutorials and PDF study guides, FAQS and jobs