ABAP Architecture...urgent

Question

Hi all,
Can any1 ans few of these ques:
1)Is the ABAP code interprted andconverted to C lang? as in thesetup we have a .dll file...
2)Is BASIS installed  only on Application server?
3)How to maintain foreignkey relationship for tables?
Thanx

Answer 1

hi,
The R/3 System allocates presentation, applications, and data storage to different computers. This
serves as the basis for the scalability of the R/3 system.
The lowest level is the database level. Here data is managed with the help of a relational database
management system (RDBMS). In addition to master data and transaction data, programs and the metadata that describe the R/3 System are stored and managed here.
ABAP programs run at the application level, both the applications provided by SAP and the ones you develop yourself. ABAP programs work with data called up from the database level and store new data there as well.
The third level is the presentation level (SAPGUI). This level contains the user interface, in which an end user can access an application, enter new data and receive the results of a work process.
ABAP programs are processed on the application server. The design of the user dialogs and the database dialogs is therefore of particular importance when writing application programs.
SAP basis
The ABAP language environment, including the syntax checking, code generation and runtime system, is part of the SAP Basis component. SAP Basis is the technological platform that supports the entire range of SAP applications, now typically implemented in the framework of the SAP Web Application Server. In that sense SAP Basis can be seen as the "operating system" on which SAP applications run. Like any operating system, SAP Basis contains both low-level services (for example memory management, database communication or servicing Web requests) and high-level tools for end users and administrators. These tools can be executables ("SAP kernel") running directly on the underlying operating system, transactions developed in ABAP, or Web-based interfaces.
SAP Basis also provides a layer of abstraction between the business applications and the operating system and database. This ensures that applications do not depend directly upon a specific server or database platform and can easily be ported from one platform to another.
SAP Basis currently runs on UNIX (AIX, HP-UX, Solaris, Linux), Microsoft Windows, i5/OS on IBM System i (formerly iSeries, AS/400) and z/OS on IBM System z (formerly zSeries, S/390). Supported databases are DB2, Informix, MaxDB, Oracle and Microsoft SQL Server (support for Informix was discontinued in SAP Basis release 7.00).
Where does the ABAP program run?
All ABAP programs reside inside the SAP database. They are not stored in separate external files like Java or C++ programs. In the database all ABAP code exists in two forms: source code, which can be viewed and edited with the ABAP Workbench tools, and generated code, a binary representation somewhat comparable with Java bytecode. ABAP programs execute under the control of the runtime system, which is part of the SAP kernel. The runtime system is responsible for processing ABAP statements, controlling the flow logic of screens and responding to events (such as a user clicking on a screen button). A key component of the ABAP runtime system is the Database Interface, which turns database-independent ABAP statements ("Open SQL") into statements understood by the underlying DBMS ("Native SQL"). The database interface handles all the communication with the relational database on behalf of ABAP programs; it also contains extra features such as buffering of frequently accessed data in the local memory of the application server.
SAP has three different layers as presentation layer (GUI), application layer (programs run on this) and data base layer where all data is stored and retrieved from user driven conditions,commands given by end user programmer through presentation layer.
For foreign key realtions.
http://help.sap.com/saphelp_nw70/helpdata/en/cf/21ea77446011d189700000e8322d00/content.htm
Hope this helps, Do reward.
Edited by: Runal Singh on Apr 23, 2008 2:22 PM