ABAP DICTIONARY INTRODUCTIOIN

The ABAP Dictionary permits a central management of all the data definitions used in the R/3 System.

In the ABAP Dictionary you can create user-defined types (data elements, structures and table types) for use in ABAP programs or in interfaces of function modules. Database objects such as tables and database views can also be defined in the ABAP Dictionary and created with this definition in the database.

The ABAP Dictionary also provides a number of services that support program development. For example, setting and releasing locks, defining an input help (F4 help) and attaching a field help (F1 help) to a screen field are supported.



Tables and database views can be defined in the ABAP Dictionary.

These objects are created in the underlying database with this definition. Changes in the definition of a table or database view are also automatically made in the database.

Indexes can be defined in the ABAP Dictionary to speed up access to data in a table. These indexes are also created in the database.


There are three different type categories in the ABAP Dictionary:

Data elements: Describe an elementary type by defining the data type, length and possibly decimal places.

Structures: Consist of components that can have any type.

Table types: Describe the structure of an internal table.

Any complex user-defined type can be built from these basic types.

Example: The data of an employee is stored in a structure EMPLOYEE with the components NAME, ADDRESS and TELEPHONE. Component NAME is also a structure with components FIRST NAME and LAST NAME. Both of these components are elementary, i.e. their type is defined by a data element. The type of component ADDRESS is also defined by a structure whose components are also structures. Component TELEPHONE is defined by a table type (since an employee can have more than one telephone number).

Types are used for example in ABAP programs or to define the types of interface parameters of function modules.


The ABAP Dictionary supports program development with a number of services:

Input helps (F4 helps) for screen fields can be defined with search helps.

Screen fields can easily be assigned a field help (F1 help) by creating documentation for the data element.

An input check that ensures that the values entered are consistent can easily be defined for screen fields using foreign keys.

The ABAP Dictionary provides support when you set and release locks. To do so, you must create lock objects in the ABAP Dictionary. Function modules for setting and releasing locks are automatically generated from these lock objects; these can then be linked into the application program.

The performance when accessing this data can be improved for database objects (tables, views) with buffering settings.
By logging, you can switch on the automatic recording of changes to the table entries.

The ABAP Dictionary is actively integrated in the development and runtime environments. Each change takes immediate effect in the relevant ABAP programs and screens.

Examples:

When a program or screen is generated, the ABAP interpreter and the screen interpreter access the type definitions stored in the ABAP Dictionary.

The ABAP tools and the Screen Painter use the information stored in the ABAP Dictionary to support you during program development. An example of this is the Get from Dictionary function in the Screen Painter, with which you can place fields of a table or structure defined in the ABAP Dictionary in a screen.

The database interface uses the information about tables or database views stored in the ABAP Dictionary to access the data of these objects.


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