Data Dictionary
The
ABAP/4 dictionary is central workbench repository utility providing the data definition
and the information relationship that are later used in all the business
application within R/3
The ABAP/4
dictionary can be seen as a logical representation or a superior layer over the
physical underlying database. This database must support the relational data
model. This model is strictly followed by data dictionary.
A Data dictionary
in computing terms is the source of information in which
system data is defined. The data dictionary is the centralized
and structured source of information for business applications. You
can say that it is core of a well-structured development environment. The
elements that make up a dictionary are known as metadata.
Metadata
is the term for the data whose function is to describe other data. Data
in dictionary is not the actual data like emp. name or emp. address but
rather a type of
data whose function is to define the properties of the data
such as type,
length, and relationship.
Advantages
Advantage of
using data dictionary is avoiding inconsistencies when defining data type that
will later be used in different applications. This avoids redundancies. When a
type is defined in the dictionary, it is available to any program in the application.
A change in the definition of a type of data in the dictionary automatically
affects any other data or program, which has this data. Again, data dictionary
is a fast and efficient way to answer questions such as which entries exist in
a table of the database, what the structure of table is.
Activation
of dictionary objects
For a dictionary
object to be effective at runtime, that is, for a dictionary object to be
available for use within a program, transaction, and so on, it must be in
active status. For objects to become active, R/3 includes the ACTIVATION
function.
When a table or
aggregated object is activated, it is placed at the disposal of the system as a
runtime object in a way that makes it available quickly for the application
program to access relevant information of new activated objects. When a
dictionary object is modified, that means that the object previously existed
and activated. You need to reactivate the object after modification. When mass
activation is performed massively, it might take a quite a long time. Then it
should be in the background system. This type of activation is known as
background activation.
The ABAP/4 Data
dictionary is the central component of ABAP/4 repository. A Data dictionary
is centralized and structured source of information for business
application. The ABAP/4 dictionary is the core of the R/3 development
system. It is the source of every definition, within R/3, from the very basic
domain to the company data model. It is totally integrated with other tools of
the development environment like screen painter, menu painter, and
editor.
Some of the main
available functions in the ABAP/4 dictionary are as follows:
¨ Add,
delete, modify, and manage the definition of the dictionary data.
¨ Preserve
the data integrity.
¨ Be
the central source of information e.g. from the dictionary you get the information
about the defined relationship between two tables or even the directory tells
whether table is active or empty.
¨ It
also permits documentation of system data.
In the R/3
system instead of working with original objects, you work with internal
representation of objects. With this type of operation the system performance is
enhanced and has the advantage that the development tools, screen
interpreters always access current data.
When any of the
data dictionary objects are used in other parts of the development
workbench for example, in program, programmer only has to enter a table
name or field name. The system automatically knows all the properties and
information of the field.
To call ABAP/4
dictionary, from the main menu, Tools ® ABAP/4 workbench
® data dictionary or enter transaction
SE11.
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