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ABAP

ABAP (Advanced Business Application Programming, originally Allgemeiner Berichts-Aufbereitungs-Prozessor = general report creation processor) is a high level programming language created by the German software company SAP. It is currently positioned, alongside the more recently introduced Java, as the language for programming SAP's Web Application Server, part of its NetWeaver platform for building business applications. Its syntax is somewhat similar to COBOL.

Introduction

ABAP is one of the many application-specific fourth-generation languages (4GLs) first developed in the 1980s. It was originally the report language for SAP R/2, a platform that enabled large corporations to build mainframe business applications for materials management and financial and management accounting.

ABAP used to be an abbreviation of Allgemeiner Berichtsaufbereitungsprozessor, the German meaning of "generic report preparation processor", but was later renamed to Advanced Business Application Programming. ABAP was one of the first languages to include the concept of Logical Databases (LDBs), which provides a high level of abstraction from the basic database level.

The ABAP programming language was originally used by developers to develop the SAP R/3 platform. It was also intended to be used by SAP customers to enhance SAP applications – customers can develop custom reports and interfaces with ABAP programming. The language is fairly easy to learn for programmers but it is not a tool for direct use by non-programmers. Good programming skills, including knowledge of relational database design and preferably also of object-oriented concepts, are required to create ABAP programs.

ABAP remains the language for creating programs for the client-server R/3 system, which SAP first released in 1992. As computer hardware evolved through the 1990s, more and more of SAP's applications and systems were written in ABAP. By 2001, all but the most basic functions were written in ABAP. In 1999, SAP released an object-oriented extension to ABAP called ABAP Objects, along with R/3 release 4.6.

SAP's most recent development platform, NetWeaver, supports both ABAP and Java.

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.

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).

SAP systems and landscapes

All SAP data exists and all SAP software runs in the context of an SAP system. A system consists of a central relational database and one or more application servers ("instances") accessing the data and programs in this database. An SAP system contains at least one instance but may contain more, mostly for reasons of sizing and performance. In a system with multiple instances, load balancing mechanisms ensure that the load is spread evenly over the available application servers.
Installations of the Web Application Server (landscapes) typically consist of three systems: one for development, one for testing and quality assurance, and one for production. The landscape may contain more systems, e.g. separate systems for unit testing and pre-production testing, or it may contain fewer, e.g. only development and production, without separate QA; nevertheless three is the most common configuration. ABAP programs are created and undergo first testing in the development system. Afterwards they are distributed to the other systems in the landscape. These actions take place under control of the Change and Transport System (CTS), which is responsible for concurrency control (e.g. preventing two developers from changing the same code at the same time), version management and deployment of programs on the QA and production systems.

The Web Application Server consists of three layers: the database layer, the application layer and the presentation layer. These layers may run on the same or on different physical machines. The database layer contains the relational database and the database software. The application layer contains the instance or instances of the system. All application processes, including the business transactions and the ABAP development, run on the application layer. The presentation layer handles the interaction with users of the system. Online access to ABAP application servers can go via a proprietary graphical interface, the SAPGUI, or via a Web browser.

Transactions

A transaction in SAP terminology is the execution of a program. The normal way of executing ABAP code in the SAP system is by entering a transaction code (for instance, SE51 is the code for the ABAP workbench). Transactions can be accessed via system-defined or user-specific, role-based menus. They can also be started by entering their transaction code (a mnemonic name of up to 20 characters) in the special command field, which is present in every SAP screen. Transactions can also be invoked programmatically by means of the ABAP statements CALL TRANSACTION and LEAVE TO TRANSACTION. Transaction codes can also be linked to screen elements or menu entries. Selecting such an element will start the transaction. The term "transaction" must not be misunderstood here: in the context just described, a transaction simply means calling and executing an ABAP program. In application programming, "transaction" often refers to an indivisible operation on data, which is either committed as a whole or undone (rolled back) as a whole. This concept exists in SAP but is there called a LUW (Logical Unit of Work). In the course of one transaction (program execution), there can be different LUWs.

Let’s have a look at the different kind of transactions:

Dialog transaction

These are the most common kind of transactions. The transaction code of a dialog transaction is linked to a Dynpro of an ABAP program. When the transaction is called, the respective program is loaded and the Dynpro is called. Therefore, a dialog transaction calls a Dynpro sequence rather than a program. Only during the execution of the Dynpro flow logic are the dialog modules of the ABAP program itself are called. The program flow can differ from execution to execution. You can even assign different dialog transaction codes to one program.

Parameter transaction

In the definition of a parameter transaction code, a dialog transaction is linked with parameters. When you call a parameter transaction, the input fields of the initial Dynpro screen of the dialog transaction are filled with parameters. The display of the initial screen can be inhibited by specifying all mandatory input fields as parameters of the transaction.

Variant transaction

In the definition of a variant transaction code, a dialog transaction is linked with a transaction variant. When a variant transaction is accessed, the dialog transaction is called and executed with the transaction variant. In transaction variants, you can assign default values to the input fields on several Dynpro screens in a transaction, change the attributes of screen elements, and hide entire screens. Transaction variants are maintained in transaction SHD0.

Report transaction

A report transaction is the transaction code wrapping for starting the reporting process. The transaction code of a report transaction must be linked with the selection screen of an executable program. When you execute a report transaction, the runtime environment internally executes the ABAP statement SUBMIT—more to come on that.

OO transaction

A new kind of transaction as of release 6.10. The transaction code of an OO transaction is linked with a method of a local or global class. When the transaction is called, the corresponding program is loaded, for instance methods an object of the class is generated and the method is executed.

Types of ABAP programs

In ABAP, there are two different types of programs:

Report programs

Report programs follow a relatively simple programming model whereby a user optionally enters a set of parameters (e.g. a selection over a subset of data) and the program then uses the input parameters to produce a report in the form of an interactive list. The output from the report program is interactive because it is not a passive display; instead it enables the user, through ABAP language constructs, to obtain a more detailed view on specific data records via drill-down functions, or to invoke further processing through menu commands, for instance to sort the data in a different way or to filter the data according to selection criteria. This method of presenting reports has great advantages for users who must deal with large quantities of information and must also have the ability to examine this information in highly flexible ways, without being constrained by the rigid formatting or unmanageable size of "listing-like" reports. The ease with which such interactive reports can be developed is one of the most striking features of the ABAP language.
The term "report" is somewhat misleading in the sense that it is also possible to create report programs that modify the data in the underlying database instead of simply reading it.

Online programs

Online programs (also called module pools) do not produce lists. These programs define more complex patterns of user interaction using a collection of screens. The term “screen” refers to the actual, physical image that the users sees. Each screen also has a “flow logic”; this refers to the ABAP code invoked by the screens, i.e. the logic that initializes screens, responds to a user’s requests and controls the sequence between the screens of a module pool. Each screen has its own Flow Logic, which is divided into a "PBO" (Process Before Output) and "PAI" (Process After Input) section. In SAP documentation the term “dynpro” (dynamic program) refers to the combination of the screen and its Flow Logic.
Online programs are not invoked directly by their name, but are associated with a transaction code. Users can then invoke them through customizable, role-dependent, transaction menus.

Apart from reports and online programs, it is also possible to develop sharable code units such as class libraries, function libraries and subroutine pools.

Subroutine pools

Subroutine pools, as the name implies, were created to contain collections of subroutines that can be called externally from other programs. Before release 6.10, this was the only way subroutine pools could be used. But besides subroutines, subroutine pools can also contain local classes and interfaces. As of release 6.10, you can connect transaction codes to methods. Therefore, you can now also call subroutine pools via transaction codes. This is the closest to a Java program you can get in ABAP: a subroutine pool with a class containing a method – say – main connected to a transaction code!

Function pools

Function pools, more commonly known as "function groups", are libraries of functions developed in ABAP. Functions differ from subroutines in that they are self-contained and do not belong to a specific program. ABAP functions accept as input any number of input parameters, return as output any number of output parameters, and raise exceptions if an error condition occurs.

Functions are invoked in ABAP programs by means of the CALL FUNCTION statement. A very important feature of ABAP is the ability to call function modules in another SAP system or in an external application using the RFC (Remote Function Call) mechanism. It is also possible to call functions asynchronously; the ABAP program then does not wait for the function to return but instead continues immediately, while the function executes in a separate context.

Type pools

Type pools are the precursors to general type definitions in the ABAP Dictionary. Before release 4.0, only elementary data types and flat structures could be defined in the ABAP Dictionary. All other types that should’ve been generally available had to be defined with TYPES in type pools. As of release 4.0, type pools were only necessary for constants. As of release 6.40, constants can be declared in the public sections of global classes and type pools can be replaced by global classes.

Class pools

Class pools serve as containers for exactly one global class. Besides the global class, they can contain global types and local classes/interfaces to be used in the global class. A class pool is loaded into memory by using one of its components. For example, a public method can be called from any ABAP program or via a transaction code connected to the method. You maintain class pools in the class builder.

Interface pools

Interface pools serve as containers for exactly one global interface—nothing more and nothing less. You use an interface pool by implementing its interface in classes and by creating reference variables with the type of its interface. You maintain interface pools in the class builder.

ABAP workbench

The ABAP Workbench contains different tools for editing Repository objects. These tools provide you with a wide range of assistance that covers the entire software development cycle. The most important tools for creating and editing Repository objects are:
ABAP Editor for writing and editing program code
ABAP Dictionary for processing database table definitions and retrieving global types
Menu Painter for designing the user interface (menu bar, standard toolbar, application toolbar, function key assignment)
Screen Painter for designing screens (dynamic programs) for user dialogs
Function Builder for displaying and processing function modules (routines with defined interfaces that are available throughout the system)
Class Builder for displaying and processing ABAP Objects classes

The ABAP dictionary

The ABAP Dictionary is a fully integrated data environment controlling facility. It contains all definitions for Domains, Data Elements, Structures, Tables, Views, Search Helps, Lock Objects, Matchcode Objects, The Table Maintenance Generator, and the Table Description Generator.

With these objects in its repository, the ABAP Dictionary:

  • Enforces data integrity
  • Manages data definitions without redundancy
  • Is tightly integrated with the rest of the ABAP/4 Development Workbench.

Enforcing data integrity is the process of ensuring that data entered into the system is logical, complete, and consistent. When data integrity rules are defined in the ABAP/4 Dictionary, the system automatically prevents the entry of invalid data. Defining the data integrity rules at the dictionary level means they only have to be defined once, rather than in each program that accesses that data.

The following are examples of data lacking integrity:

  • A date field with a month value of 13
  • An order assigned to a customer number that doesn’t exist
  • An order not assigned to a customer

Managing data definitions without redundancy is the process of linking similar information to the same data definition. For example, a customer database is likely to contain a customer’s ID number in several places. The ABAP Dictionary provides the capability of defining the characteristics of a customer ID number in only one place. That central definition then can be used for each instance of a customer ID number.

The ABAP Dictionary’s integration with the rest of the development environment enables ABAP programs to automatically recognize the names and characteristics of dictionary objects.

Additionally, the system provides easy navigation between development objects and dictionary definitions. For example, as a programmer, you can double-click on the name of a dictionary object in your program code, and the system will take you directly to the definition of that object in the ABAP/4 Dictionary.

When a dictionary object is changed, a program that references the changed object will automatically reference the new version the next time the program runs. Because ABAP is interpreted, it is not necessary to recompile programs that reference changed dictionary objects.

ABAP syntax

This brief description of the ABAP syntax begins inevitably with the ubiquitous "Hello World" program.

"Helloworld"

PROGRAM TEST.
WRITE 'Hello World'.
This example contains two statements, one on each line. The keywords are PROGRAM and WRITE. The program displays a list on the screen. In this case, the list consists of the line "Hello World".

Formatting rules

White space significance

ABAP has no format restrictions. You can enter statements in any format, so a statement can be indented, you can write several statements on one line, or spread a single statement over several lines. The only requirement is that every statement ends in a period.

You must separate words within a statement with at least one space. The system also interprets the end of line marker as a space.

The two-line "Hello World" program from above could also be written as

PROGRAM TEST. WRITE 'Hello World' .
or even as:
              PROGRAM
              TEST.
                         WRITE
                         'Hello World'.
Free formatting is convenient, but with complex code, such as deeply nested IF/ELSE blocks, it can get tricky. The ABAP editor therefore offers a "Pretty Printer" function, which can take care of proper indentation.

One obvious exception to the free-formatting rule are text literals. A text literal is a sequence of alphanumeric characters in the program code enclosed in single quotes. If a text literal in an ABAP statement extends across more than one line, then a ‘&’ character must be used to combine a succession of text literals into a single one. Example:

USERPROMPT = 'Please double-click on a line in the output list ' &
            'to see the complete details of the transaction.'.

Case sensitivity

ABAP statements are not case-sensitive. The following code is perfectly permissible:
proGRAm TEsT.
WriTe 'Hello World'.
Users can configure the way source text is presented (all upper case, all lower case, ABAP keywords in upper case and variable names in lower case, etc.) according to their own preference.

Chained statements

The ABAP programming language allows you to concatenate consecutive statements with an identical first part into a chain statement.

To concatenate a sequence of separate statements, write the identical part only once and place a colon (:) after it. After the colon, write the remaining parts of the individual statements, separating them with commas. Ensure that you place a period (.) after the last part to inform the system where the chain ends.

Chaining is very often used in WRITE statements. WRITE accepts just one argument, so if for instance you wanted to display three fields from a structure called FLIGHTINFO, you would have to code:

WRITE FLIGHTINFO-CITYFROM.
WRITE FLIGHTINFO-CITYTO.
WRITE FLIGHTINFO-AIRPTO.
Chaining the statements results in a more readable and more intuitive form:

WRITE: FLIGHTINFO-CITYFROM, FLIGHTINFO-CITYTO, FLIGHTINFO-AIRPTO.

In the chain, a colon separates the beginning of the statement from the variable parts. After the colon or commas, you can insert any number of spaces.

You could, for example, write the same statement like this:

WRITE:    FLIGHTINFO-CITYFROM,
         FLIGHTINFO-CITYTO,
         FLIGHTINFO-AIRPTO.
In a chain statement, the first part (before the colon) is not limited to the keyword of the statements. For example, the code
SUM = SUM + 1.
SUM = SUM + 2.
SUM = SUM + 3.
SUM = SUM + 4.
could be written in chained form:
SUM = SUM + : 1, 2, 3, 4.

Comments

ABAP has 2 ways of defining text as a comment.

An asterisk (>>*<<) in the leftmost column of a line makes that line a comment. A double quotation mark (>>"<<) anywhere on a line makes the rest of that line a comment.

Example

  • *
  • Program: BOOKINGS **
  • Author: Joe Byte, 07-Jul-2007 **
    • *

    REPORT BOOKINGS.

    • Read flight bookings from the database

    SELECT * FROM FLIGHTINFO

     WHERE CLASS = 'Y'       "Y = economy
     OR    CLASS = 'C'.      "C = business
    (...)

    Naming notation

    ABAP has a large number of naming conventions for different language elements. These are conventions and not rules, so an ABAP programmer is free to abide by them or not. However ABAP code developed by SAP itself generally respects these naming rules. Below is a list.

    • ALV_* Advance list viewer
    • AS_* Methods that perform type conversions
    • CHECK_* Check Methods
    • CH_* Changing Parameters
    • CL_* Class name
    • CO_*/C_* Constants
    • DR_* Data reference
    • G_* Global variables/data objects
    • GT_* Global table
    • GX_* Global boolean field (X or space)
    • IF_* Interface
    • INT_*/IT_ Internal Table
    • IS_* Methods that return a Boolean value
    • L_* Indicates the data object is local. Often, before underscore, put a 'type letter' in case of simple type (LC_,LF etc.)
    • LC_* Local Constant
    • LR_* Local Range
    • LT_* Local Table
    • LVC_* List Viewer Control
    • ON_* Event handler
    • PA_* Parameters
    • PE_*/EX_* Export parameter
    • PI_*/IM_* Input parameter
    • RA_* Ranges/Type Range Of
    • RE_* Result
    • RF_* Reference Variable
    • SET_* Accessors Methods
    • SO_* Select-Options
    • ST_* Structure
    • TA_* Internal Standard Table
    • TC_* Table Control
    • TH_* Internal Hashed Table
    • TP_* Other Variables
    • TS_* Internal Sorted Table
    • TT_* Table type
    • TY_* Types
    • T_* Variable is a table (T_MY_TABLE_VARIABLE)
    • X* Source/first data object (e.g. XVBAK)
    • Y* Destination/second data object (e.g. YVBAK)
    • WA_* Working Area
    • ** Secondary working area (e.g. *VBAK in TABLES statement. Obsolete)

    DATA and TYPES

    It is a special strength of ABAP that you can define a great variety of data types and objects that span the spectrum from very elementary data types to very complex and dynamic types. Consequently, the subject of ABAP declarations is quite extensive.

    ABAP accepts all data types defined in the SAP dictionary or in Type Pools. Types can also be defined inside the program itself. Object numeric (I for integer, F for floating point), packed decimal (P), character (C or N, where the N type is used for numeric strings that can be used in computation) or hexadecimal (X). Date fields (type D) and time fields (type T) have a "dual" nature; in an input/output context they behave like strings, but in a computational context they are numeric integers. This makes date and time calculations extremely easy. For example:

    DATESENT = '20070901'.
    VALIDTO = DATESENT + 60.
    WRITE: 'Offer is valid until', VALIDTO DD/MM/YYYY.
    
    In this example, a string literal representing September 1, 2007 is assigned to DATESENT. DATESENT is then used in a numeric calculation to produce another data field, VALIDTO. VALIDTO is then output as a string. The optional "DD/MM/YYYY" modifier displays the date in a predefined format, here "31/10/2007". Without the modifier the date would display as "20071031".

    All ABAP variables must be explicitly declared in order to be used. The convention is for all declarations to be at the top of the program, or subroutine. The declaration consists of the name, type, length (where applicable), additional modifiers (e.g. the number of implied decimals for a packed decimal field) and optionally an initial value:

    • Primitive types:

    DATA: COUNTER TYPE I,

         VALIDITY     TYPE I VALUE 60,
         TAXRATE(3)   TYPE P DECIMALS 1,
         LASTNAME(20) TYPE C.

    • Dictionary types:

    DATA: ORIGIN TYPE COUNTRY.

    • Internal table:

    DATA: T_FLIGHTS TYPE TABLE OF FLIGHTINFO,

         T_LOOKUP     TYPE HASHED TABLE OF FLT_LOOKUP.

    • Objects:

    DATA: BOOKING TYPE REF TO CL_FLT_BOOKING.

    Notice the use of the colon to chain together consecutive DATA statements.

    ABAP Objects

    Object orientation in ABAP is an extension of the ABAP language that makes available the advantages of object-oriented programming, such as encapsulation, interfaces, and inheritance. This helps to simplify applications and make them more controllable.

    ABAP Objects is fully compatible with the existing language, so you can use existing statements and modularization units in programs that use ABAP Objects, and can also use ABAP Objects in existing ABAP programs. Note, however, that syntax checking is stronger in ABAP Objects programs, and some syntactical forms (usually older ones) of certain statements are not permitted.

    ABAP statements – an overview

    The first element of an ABAP statement is the ABAP keyword. This determines the category of the statement. The different statement categories are as follows:

    Declarative statements

    These statements define data types or declare data objects which are used by the other statements in a program or routine. The collected declarative statements in a program or routine make up its declaration part.

    Examples of declarative keywords:

    TYPES, DATA, TABLES

    Modularization statements

    These statements define the processing blocks in an ABAP program.

    The modularization keywords can be further divided into:

    · Event Keywords

    You use statements containing these keywords to define event blocks. There are no special statements to conclude processing blocks - they end when the next processing block is introduced.

    Examples of event keywords are:

    AT SELECTION SCREEN, START-OF-SELECTION, AT USER-COMMAND

    · Defining keywords

    You use statements containing these keywords to define subroutines, function modules, dialog modules and methods. You conclude these processing blocks using the END- statements.

    Examples of definitive keywords:

    FORM ..... ENDFORM, FUNCTION ... ENDFUNCTION, MODULE ... ENDMODULE. '''

    Control statements

    You use these statements to control the flow of an ABAP program within a processing block according to certain conditions.

    Examples of control keywords:

    IF, WHILE, CASE

    Call statements

    You use these statements to call processing blocks that you have already defined using modularization statements. The blocks you call can either be in the same ABAP program or in a different program.

    Examples of call keywords:

    CALL METHOD, CALL TRANSACTION, SUBMIT, LEAVE TO

    Operational statements

    These keywords process the data that you have defined using declarative statements.

    Examples of operational keywords:

    MOVE, ADD

    Unique concept of internal table in ABAP

    Internal tables provide a means of taking data from a fixed structure and storing it in working memory in ABAP. The data is stored line by line in memory, and each line has the same structure. In ABAP, internal tables fulfill the function of arrays. Since they are dynamic data objects, the programmer is saved the task of dynamic memory management in his or her programs. Internal tables should be used whenever there is a need to process a dataset with a fixed structure within a program. A particularly important use for internal tables is for storing and formatting data from a database table within a program. They are also a good way of including very complicated data structures in an ABAP program.

    Like all elements in the ABAP type concept, internal tables can exist both as data types and as data objects. A data type is the abstract description of an internal table, either in a program or centrally in the ABAP Dictionary, that you use to create a concrete data object. The data type is also an attribute of an existing data object.

    Internal tables as data types

    Internal tables and structures are the two structured data types in ABAP. The data type of an internal table is fully specified by its line type, key, and table type.

    Line type

    The line type of an internal table can be any data type. The data type of an internal table is normally a structure. Each component of the structure is a column in the internal table. However, the line type may also be elementary or another internal table.

    Line Type can also refer to an ABAP Object's reference pointer value. If two ABAP Objects are not related, they do not have the same line type. The line type is stored in the value of the reference pointer and can be viewed in the debugger. If one object attempts to access another unrelated object's components, you will receive an error specifying that the line types do not match.

    Key

    The key identifies table rows. There are two kinds of key for internal tables - the standard key and a user-defined key. You can specify whether the key is UNIQUE or NON-UNIQUE. Internal tables with a unique key cannot contain duplicate entries with the same key. The uniqueness depends on the table access method.

    If a table has a structured line type, its default key consists of all of its non-numerical columns that are not references or themselves internal tables. If a table has an elementary line type, the default key is the entire line. An internal table which has a line type that is itself an internal table, has an empty key.

    The user-defined key can contain any columns of the internal table that are not references or themselves internal tables. Internal tables with a user-defined key are called key tables. When you define the key, the sequence of the key fields is significant. You should remember this, for example, if you intend to sort the table according to the key.

    Later versions of ABAP permit the definition of secondary keys.

    Table type

    The table type determines how ABAP will access individual table entries. Internal tables can be divided into three types:

    Standard tables have an internal linear index. (Think of index as "record number". It is not to be confused with a database index, for example). From a particular size upwards, the indexes of internal tables are administered as trees. In this case, the index administration overhead increases in logarithmic and not linear relation to the number of lines. The system can access records either by using the table index or the key. The response time for key access is proportional to the number of entries in the table. The key of a standard table is always non-unique. You cannot specify a unique key. This means that standard tables can always be filled very quickly, since the system does not have to check whether there are already existing entries.

    Sorted tables are always saved sorted by the key. They also have an internal index. The system can access records either by using the table index or the key. The response time for key access is logarithmically proportional to the number of table entries, since the system uses a binary search. The key of a sorted table can be either unique or non-unique. When you define the table, you must specify whether the key is to be unique or not. Standard tables and sorted tables are known generically as index tables.

    Hashed tables have no linear index. You can only access a hashed table using its key. The response time is independent of the number of table entries, and is constant, since the system access the table entries using a hash algorithm. The key of a hashed table must be unique. When you define the table, you must specify the key as UNIQUE.

    Generic internal tables

    Unlike other local data types in programs, you do not have to specify the data type of an internal table fully. Instead, you can specify a generic construction, that is, the key or key and line type of an internal table data type may remain unspecified. You can use generic internal tables to specify the types of field symbols and the interface parameters of procedures. You cannot use them to declare data objects.

    Internal tables as dynamic data objects

    Data objects that are defined either with the data type of an internal table, or directly as an internal table, are always fully defined in respect of their line type, key and access method. However, the number of lines is not fixed. Thus internal tables are dynamic data objects, since they can contain any number of lines of a particular type. The only restriction on the number of lines an internal table may contain are the limits of your system installation. The maximum memory that can be occupied by an internal table (including its internal administration) is 2 gigabytes. A more realistic figure is up to 500 megabytes. An additional restriction for hashed tables is that they may not contain more than 2 million entries. The line types of internal tables can be any ABAP data types - elementary, structured, or internal tables. The individual lines of an internal table are called table lines or table entries. Each component of a structured line is called a column in the internal table.

    Choosing a table type

    The table type (and particularly the access method) that you will use depends on how the typical internal table operations will be most frequently executed.

    Standard tables

    This is the most appropriate type if you are going to address the individual table entries using the index. Index access is the quickest possible access. You should fill a standard table by appending lines (ABAP APPEND statement), and read, modify and delete entries by specifying the index (INDEX option with the relevant ABAP command). The access time for a standard table increases in a linear relationship with the number of table entries. If you need key access, standard tables are particularly useful if you can fill and process the table in separate steps. For example, you could fill the table by appending entries, and then sort it. If you use the binary search option with key access, the response time is logarithmically proportional to the number of table entries.

    Sorted tables

    This is the most appropriate type if you need a table which is sorted as you fill it. You fill sorted tables using the INSERT statement. Entries are inserted according to the sort sequence defined through the table key. Any illegal entries are recognized as soon as you try to add them to the table. The response time for key access is logarithmically proportional to the number of table entries, since the system always uses a binary search. Sorted tables are particularly useful for partially sequential processing in a LOOP if you specify the beginning of the table key in the WHERE condition.

    Hashed tables:

    This is the most appropriate type for any table where the main operation is key access. You cannot access a hashed table using its index. The response time for key access remains constant, regardless of the number of table entries. Like database tables, hashed tables always have a unique key. Hashed tables are useful if you want to construct and use an internal table which resembles a database table or for processing large amounts of data.

    Advanced topics

    Batch input: concepts

    Processing sessions

    A batch input session is a set of one or more calls to transactions along with the data to be processed by the transactions. The system normally executes the transactions in a session non-interactively, allowing rapid entry of bulk data into an R/3 System.

    A session records transactions and data in a special format that can be interpreted by the R/3 System. When the System reads a session, it uses the data in the session to simulate on-line entry of transactions and data. The System can call transactions and enter data using most of the facilities that are available to interactive users.

    For example, the data that a session enters into transaction screens is subject to the same consistency checking as in normal interactive operation. Further, batch input sessions are subject to the user-based authorization checking that is performed by the system.

    There are three batch input methods:

    (1) In the Direct Input Method, the programs are provided by the SAP system. These programs are available for Standard Applications. Under this method, the data base is updated using a Function Module, which is responsible for executing the appropriate consistency checks.

    (2) In the Call Transaction Method, the ABAP Program reads the external data which is present on the Application or Presentation Server, and uses the ABAP Statement CALL TRANSACTION USING to run a SAP statement.

    (3) In the Session Method the program reads the data and the SAP system stores the data in a "Batch Input Session". The session records the actions that are required to transfer data into the system using normal SAP transactions.

    Advantages of ABAP over contemporary languages

    ABAP Objects offers a number of advantages, even for procedural programming. Many advanced features of ABAP use object-oriented interfaces.

    Sharing Data: With ABAP shared objects, you can aggregate data in memory once at a central location. Different users and programs can then access this data without the need for copying.

    Exception Handling: With the class-based exception concept of ABAP, you can define a special control flow for a specific error situation and provide the user with information about the error.

    Developing Persistency: For permanent storage of data in ABAP, you use relational database tables by means of database-independent Open SQL, which is integrated in ABAP. However, you can also store selected objects transparently or access the integrated database or other databases using proprietary SQL.

    Connectivity and Interoperability: The Exchange Infrastructure and Web services are the means by which developers can implement a service-oriented architecture. With Web services, you can provide and consume services independently of implementation or protocol. Furthermore, you can do so within NetWeaver and in the communication with other systems. With the features of the Exchange Infrastructure, you can enable, manage, and adapt integration scenarios between systems.

    Making Enhancements: With the Enhancement Framework, you can enhance programs, function modules, and global classes without modification as well as replace existing code. The Switch Framework enables you activate only specific development objects or enhancements in a system.

    Example

    From SAP NetWeaver:
    *-----------------------------------------------------------------------
    * set an exclusive lock at level object-type & object-id
    *-----------------------------------------------------------------------
      IF NOT lf_bapi_error = true.
        IF ( NOT istourhd-doc_type IS INITIAL ) AND
           ( NOT istourhd-doc_id IS INITIAL )
    
          CALL FUNCTION 'ENQUEUE_/DSD/E_HH_RAREF'
               EXPORTING
                    obj_typ        = istourhd-doc_type
                    obj_id         = istourhd-doc_id
               EXCEPTIONS
                    foreign_lock   = 1
                    system_failure = 2
                    OTHERS         = 3.
          IF sy-subrc <> 0.
    *       terminate processing...
            lf_bapi_error = true.—
    *       ...and add message to return table
            PERFORM set_msg_to_bapiret2
                 USING    sy-msgid gc_abort sy-msgno
                          sy-msgv1 sy-msgv2 sy-msgv3 sy-msgv4
                          gc_istourhd gc_enqueue_refdoc space
                 CHANGING lt_return.
          ENDIF.
        ENDIF.
      ENDIF.    " bapi error
    

    Example report(type - ALV(ABAP list viewer))

    REPORT Z_ALV_SIMPLE_EXAMPLE_WITH_ITAB .
    ************************************************************************
    *Simple example to use ALV and to define the ALV data in an internal
    *table
    ************************************************************************
    *data definition
    
    tables:
    marav. "Table MARA and table MAKT
    
    *---------------------------------------------------------------------*
    * Data to be displayed in ALV
    * Using the following syntax, REUSE_ALV_FIELDCATALOG_MERGE can auto-
    * matically determine the fieldstructure from this source program
    Data:
    begin of imat occurs 100,
    matnr like marav-matnr, "Material number
    maktx like marav-maktx, "Material short text
    matkl like marav-matkl, "Material group (so you can test to make
                            " intermediate sums)
    ntgew like marav-ntgew, "Net weight, numeric field (so you can test to
                            "make sums)
    gewei like marav-gewei, "weight unit (just to be complete)
    end of imat.
    
    *---------------------------------------------------------------------*
    * Other data needed
    * field to store report name
    data i_repid like sy-repid.
    * field to check table length
    data i_lines like sy-tabix.
    
    *---------------------------------------------------------------------*
    * Data for ALV display
    TYPE-POOLS: SLIS.
    data int_fcat type SLIS_T_FIELDCAT_ALV.
    
    *---------------------------------------------------------------------*
    select-options:
    s_matnr for marav-matnr matchcode object MAT1.
    
    *---------------------------------------------------------------------*
    start-of-selection.
    
    * read data into table imat
      select * from marav
      into corresponding fields of table imat
      where
      matnr in s_matnr.
    
    * Check if material was found
      clear i_lines.
      describe table imat lines i_lines.
      if i_lines lt 1.
    *   Using hardcoded write here for easy upload
        write: /
        'No materials found.'.
        exit.
      endif.
    
    end-of-selection.
    
    * To use ALV, we need either a reference to a structure defined in
    * the SAP Data Dictionary (DDIC) or an in-program structure called
    * the Field Catalog.
    * The Field Catalog can be declared explicitly or generated by FUNCTION
    * 'REUSE_ALV_FIELDCATALOG_MERGE' from an internal table from any
    * report source, including this report.
    *---------------------------------------------------------------------*
    
    * Store report name
      i_repid = sy-repid.
    
    * Create Fieldcatalogue from internal table
      CALL FUNCTION 'REUSE_ALV_FIELDCATALOG_MERGE'
           EXPORTING
                I_PROGRAM_NAME         = i_repid
                I_INTERNAL_TABNAME     = 'IMAT'  "capital letters!
                I_INCLNAME             = i_repid
           CHANGING
                CT_FIELDCAT            = int_fcat
           EXCEPTIONS
                INCONSISTENT_INTERFACE = 1
                PROGRAM_ERROR          = 2
                OTHERS                 = 3.
    *explanations:
    *    I_PROGRAM_NAME is the program which calls this function
    *
    *    I_INTERNAL_TABNAME is the name of the internal table which you want
    *                       to display in ALV
    *
    *    I_INCLNAME is the ABAP-source where the internal table is defined
    *               (DATA....)
    *      CT_FIELDCAT contains the Fieldcatalouge that we need later for
    *      ALV display
    
    
      IF SY-SUBRC <> 0.
        write: /
        'Returncode',
        sy-subrc,
        'from FUNCTION REUSE_ALV_FIELDCATALOG_MERGE'.
      ENDIF.
    
    *This was the field catalog
    *---------------------------------------------------------------------*
    *
    
    * Call for ALV list display
      CALL FUNCTION 'REUSE_ALV_LIST_DISPLAY'
           EXPORTING
                I_CALLBACK_PROGRAM = i_repid
                IT_FIELDCAT        = int_fcat
           TABLES
                T_OUTTAB           = imat
           EXCEPTIONS
                PROGRAM_ERROR      = 1
                OTHERS             = 2.
    
    *explanations:
    *    I_CALLBACK_PROGRAM is the program which calls this function
    *
    *    IT_FIELDCAT (just made by REUSE_ALV_FIELDCATALOG_MERGE) contains
    *                 now the data definition needed for display
    *
    *    I_SAVE allows the user to save his own layouts
    *
    *      T_OUTTAB contains the data to be displayed in ALV
    
    
      IF SY-SUBRC <> 0.
        write: /
        'Returncode',
        sy-subrc,
        'from FUNCTION REUSE_ALV_LIST_DISPLAY'.
      ENDIF.
    
    
    

    See also

    External links

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