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Client / server architecture

Sample program with data displayed in list form

Sample program with data displayed on a screen

Which ABAP program components are discussed in

which units?

Contents:

Program low in an ABAP Program

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Client / server architectureClient / server architecture

Sample program with data displayed in list formSample program with data displayed in list form

Sample program with data displayed on the screenSample program with data displayed on the screen

Which ABAP program components are discussedWhich ABAP program components are discussed

in which units?in which units?

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Client / Server Architecture

Presentation

Server

%ayer

Application

Server

%ayer

data&ase

'ispatcher

Wor(Process

SAP)*+ SAP)*+ SAP)*+ SAP)*+ SAP)*+ SAP)*+

Wor(Process

Wor(Process

Wor(Process

'ispatcher

Wor(

Process

Wor(

Process

Wor(

Process

Wor(

Process

The R/3 System has a modular software architecture that follows software-oriented client/server

principles.

The R/3 System allocates presentation, applications, and data storage to different computers. This

serves as the basis for the scalabilityof the R/3 system.

The lowest level is the database level. Here data is managed with the help of a relational database

management system (R!"S#. $n addition to master data and transaction data, programs and the

metadata that describe the R/3 System are stored and managed here.

%!%& programs run at the application level, both the applications provided by S%& and the ones

you develop yourself. %!%& programs wor' with data called up from the database level and store

new data there as well. The third level is the presentation level (S%&)$#. This level contains the user interface, in which

an end user can access an application, enter new data and receive the results of a wor' process.

The technical distribution of software is independent of its physical location on the hardware.

*ertically, all levels can be installed on top of each other on one computer or each level on a separate

computer. Hori+ontally, application and presentation level components can be divided among any

number of computers. The hori+ontal distribution of database components, however, depends on the

type of database installed.

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*ser-#riented .iew

Presentation

Server

%ayer

Application

Server

%ayer

'ata&ase

Wor( Process

ABAP Program

This graphic can be simplified for most topics discussed during this course. The interaction between

%!%& programs and their users will be of primary interest to us during this course. The eact

processes involved in user dispatching on an application server are secondary to understanding how

to write an %!%& program. Therefore we will be wor'ing with a simplified graphic that does not

eplicitly show the dispatcher and the wor' process. -ertain slides will, however, be enhanced to

include these details whenever they are relevant to %!%& programming.

%!%& programs are processed on the application server. The design of the user dialogsand the

database dialogsis therefore of particular importance when writing application programs.

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Program low: What the *ser Sees

ime

Selection Screen

%ist

Blac

(Bo1

Screen

The user is primarily interested in how his or her business transaction flows and in how data can be

input into and displayed from the transaction. Technical details, such as whether a single program is

running or multiple programs are called implicitly, or the technical differences between the 'ind of

screens being displayed, are usually less important to the user. The user does not need to 'now the

precise flow of the %!%& program on the application server. )sers see the R/3 System with

application servers and database as a blac' bo.

There are, however, three technically distinct screen types (screens, selection screens, and lists# that

offer the user different services. $t is the developers ob to determine which type of user dialog is

most suitable to the users needs.

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+nteraction Between Server %ayers

Program

Start

ABAP 3untime System

ABAP Program

ABAP

Processing

Bloc(

ABAPProcessing

Bloc(

'ata&ase

a&le

0hen the user performs a user action (choosingEnter,a function 'ey, a menu function or a

pushbutton, for eample#, control is handed over from the presentation server to the application

server and certain parts of the %!%& program are processed. $f further user dialog is triggered within

the %!%& program, the system sends a screen to the presentation server and control is once again

handed over to the presentation server.

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$n this part of the unit, the user has chosen to start a program where an airline $ can be entered on

the initial selection screen. The program subse1uently uses this information to retrieve the 2ong

name of airline and the 2ocal currency of airline from the database and display them for the user in

list form.

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Program

Start

Sample Program 6: Program Start

'ata&ase

a&le

3epository

ime

0henever a user logs on to the system, a screen is displayed. rom this screen, the user can start a

program by using its menu path.

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Program

Start

System %oads Program Conte1t

'ata #&8ects

ABAPProcessing

Bloc(

ABAP 3untime System

ABAP Program

Selection Screen

3epository

'ata&ase

a&le

$f the user has triggered a program with a user action, then the program contet is loaded on the

application server. The program contet contains memory areas for variables and comple data

obects, information on the screens for user dialogs and %!%& processing bloc's. The runtime

system gets the program information from the Repository, which is a special part of the database.

The sample program has a selection screen as the user dialog, a variable and a structure as data

obects and one %!%& processing bloc'. The list that is used to display the data is created

dynamically at runtime.

The subse1uent flow of the program is controlled by the %!%& runtime system.

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Program

Start

3untime System Sends Selection Screen

'ata #&8ects

ABAPProcessing

Bloc(

ABAP 3untime System

ABAP Program

'ata&ase

a&le

Since the program contains a selection screen, the %!%& runtime system sends it to the presentation

server at the beginning of program processing. The presentation server controls the program flow for

as long as the user fills in the input fields.

Selection screens allow users to enter selection criteria re1uired by the program.

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Program

Start

Selection Screen 9ntries +nserted into 'ata #&8ects

'ata o&8ects

ABAPProcessing

Bloc(

ABAP 3untime System

ABAP Program

'ata&ase

a&le

%s soon as the user has finished entering data on the selection screen, he or she can trigger further

processing by choosing 4ecute. %ll data input on the selection screen is the automatically placed in

its corresponding data obect in the program and the %!%& runtime system resumes control of

processing. 5ur sample program contains only one %!%& processing bloc'. The runtime system

triggers se1uential processing of this %!%& processing bloc'.

$f the entries made by the user do not have the correct type, then an error message is automatically

triggered. The user must correct his/her entries.

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Program

Start

Program 3euests 'ata 3ecord from 'ata&ase

'ata&ase

a&le

ABAPProcessing

Bloc(

ABAP 3untime System

ABAP Program

'ata o&8ects

The %!%& processing bloc' contains a read access to the database that has been programmed into it.

The program also passes the database information about which database table to access and which

line in the table to read.

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Program

Start

'ata&ase 3eturns 'ata 3ecord to Program

'ata&ase

a&le

'ata o&8ects

ABAPProcessing

Bloc(

ABAP 3untime System

ABAP Program

The database returns the re1uested data record to the program and the runtime system ensures that

this data is stored in the appropriate data obects. 6ormally a structure is the target field when a

single record is accessed. The structure contains variables for all fields re1uested from the database.

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Program

Start

3untime System Sends %ist

'ata&ase

a&le

'ata o&8ects

ABAPProcessing

Bloc(

ABAP 3untime System

ABAP Program

The layout of the subse1uent list display has also been programmed into the processing bloc'. %fter

all processing has ended, the runtime system sends the list screen to the presentation server.

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$n this part of the unit, the user starts a second sample program where an airline $ can be entered on

the initial selection screen. This program subse1uently uses the information input on the selection

screen to retrieve the 2ong name of airline and the 2ocal currency of airline from the database and

display them for the user on a screen.

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Sample Program ": Program Start

'ata&ase

a&le

'ata o&8ects

ABAP

Processing

Bloc(

ABAP 3untime System

ABAP ProgramProgram

Start3epository

Screen

0hen the user starts the program, the program contet is loaded first. This time, however, our

sample program contains three processing bloc's, a selection screen, and a screen, and a variable and

two structures as its data obects.

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'ata&ase

a&le

'ata o&8ects

ABAP

Processing

Bloc(

ABAP 3untime System

ABAP ProgramProgram

Start

Screen

ABAP 3untime System sends Screen

Since the program contains a selection screen, the %!%& runtime system sends it to the presentation

server at the beginning of program processing.

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*ser %eaves Selection Screen

'ata&ase

a&le

'ata o&8ects

ABAP

Processing

Bloc(

ABAP 3untime System

ABAP ProgramProgram

Start

Screen

%s soon as the user has finished entering data on the selection screen, he or she can trigger further

processing by choosing 4ecute. %ll data input on the selection screen is then automatically placed

in its corresponding data obect in the program and the %!%& runtime system resumes control of

processing. The runtime system then triggers se1uential processing of the %!%& processing bloc'

that comes after the selection screen.

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Program 3euests 'ata 3ecord from 'ata&ase

'ata&ase

a&le

'ata o&8ects

ABAP

Processing

Bloc(

ABAP 3untime System

ABAP ProgramProgram

Start

Screen

The %!%& processing bloc' contains a read access to the database that has been programmed into it.

The program also passes the database information about which database table to access and which

line in the table to read.

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'ata&ase 3eturns 'ata 3ecord

'ata&ase

a&le

'ata o&8ects

ABAP

Processing

Bloc(

ABAP 3untime System

ABAP ProgramProgram

Start

Screen

The database returns the re1uested data record to the program and the runtime system ensures that

this data is stored in the appropriate data obects. 6ormally a structure is the target field when a

single record is accessed. The structure contains variables for all fields re1uested from the database.

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Screen

ime

Program Calls Screen

'ata&ase

a&le

'ata o&8ects

ABAP

Processing

Bloc(

ABAP 3untime System

ABAP Program

Process

Before#utput

Program

Start

The %!%& processing bloc' now triggers screen processing. This is often epressed simply by

saying The program calls the screen. However, in reality, each screen possesses its own processing

bloc' that is se1uentially processed before the runtime system sends the screen to the presentation

server (Process Before Output#. This allows screens to be used in a very fleible manner.

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ABAP 3untime System Sends Selection Screen

'ata&ase

a&le

'ata o&8ects

ABAP

Processing

Bloc(

ABAP 3untime System

ABAP ProgramProgram

Start

Screen

Process

Before#utput

%fter the screens processing bloc' has been processed, the %!%& runtime system sends the screen to

the presentation server. uring this process, data is transported into the screens fields from a

structure that serves as an interface for the screen.

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*ser 91ecutes *ser Action

'ata&ase

a&le

'ata o&8ects

ABAP

Processing

Bloc(

ABAP 3untime System

ABAP ProgramProgram

Start

Screen

Process

Before#utput

Process

After

+nput

5nce the user performs a user action (choosingEnter, a function 'ey, a menu function or a

pushbutton, for eample#, control is handed over to the runtime system on the application server

again. The screen fields are transported into the structure that serves as the screens interface and a

special processing bloc' belonging to the screen is triggered. This processing bloc' is always

processed immediately following a user action (Process After Input#.

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Processing of the ABAP Processing Bloc(3esumes

'ata&ase

a&le

'ata o&8ects

ABAP

Processing

Bloc(

ABAP 3untime System

ABAP ProgramProgram

Start

Screen

Process

Before#utput

Process

After

+nput

%fter the &rocess %fter $nput processing bloc' has been processed, the sample program continues

processing the %!%& processing bloc' that called the screen in the first place.

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Unit 1 +ntroduction

Unit 2 Program low in an ABAP Program

Unit 3 +ntroduction to the ABAP Wor(&ench

Unit 4 ABAP Statements and 'ata 'eclarations

Unit 5 'ata&ase 'ialogs + ;3eading from the 'ata&aseation

Unit 7 *ser 'ialogs: %ist

Unit 8 *ser 'ialogs: Selection Screen

Unit 9 *ser 'ialogs: Screen

Unit 10 +nterfaces

Course Content

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Unit 11 3euse Components

Unit 12 'ata&ase 'ialogs ++ ;=a(ing Changes to the 'ata&ase

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