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Data Dictionary, also known as 'metadata repository', is a "central repository of information about data such as meaning, relationship to other data, origin, usage, and format". ABAP Dictionary centrally describes and manages all the data definitions used in the system and the database. It is completely integrated in the ABAP Development Workbench. All the other components present in the workbench actively access the definitions stored in the data dictionary. ABAP Dictionary supports the definition of user-defined types i.e. data elements, structures and table types. These types are used in the ABAP processors and ABAP programs. It also defines the structure of database objects i.e. tables, views and indexes. These database objects automatically get created in the underlying database with the definition of data dictionary when the objects are activated. It also provides editing tools like Search help and locking tool such as lock objects. Thus, objects present in the ABAP Dictionary are tables, views, types (data elements, structures and table types), domain, search helps and lock objects.
Objects in Data Dictionary
Objects created in the ABAP Dictionary are created in the underlying relational database using these data
definitions. The ABAP dictionary thus describes the logical structure of the object used in the application
development and shows how they are mapped to the underlying relational database in table or view. As
discussed, most important object types in the ABAP dictionary are tables, views, types, domains, search
helps and lock objects.
Tables:
Tables are defined independently of the database. First the table structure is created in the ABAP dictionary
then the table is created in the underlying database from this structure.
Views:
Views combines more than one table. The structure of the view is defined in the ABAP Dictionary. With the
help of views, application-dependent view can be defined that combines the data.
Types:
Types are generally used in ABAP programs and ABAP dictionary to define the structure of the fields,
variables, constants, tables, etc. Types can be further classified as elementary types, reference types or
complex types. Data element, structure and table types are the type categories under user defined data
types.
Domains:
Domain is a central object which defines the technical attribute of a field. Technical attribute refers to data
type, length, fixed value and interval of a field (field of the table, structure, table type etc.). Domain is
assigned to the data element which in turn is assigned to the table fields or structure fields. So all the fields
which use the data element have the technical settings defined by the domain.
Search Helps:
With search help user can display the list of all possible input values for a screen field. Whenever 'F4' key is
pressed on the screen field, popup will appear having the list of entries which satisfies the search in that
screen field. You can select the needed record. There are three types of search help, 'elementary search
helps', 'collective search helps' and 'Append search helps'.
Lock objects:
In R/3 system, multiple users can access same object simultaneously. When one person is editing the
program/transaction, locks are set so that no other person can make changes to that program at the same
time. Function modules are generated automatically from the lock object definition of ABAP Dictionary.
These function modules are responsible to enqueue or dequeue the locks on the objects.
Data Types
Global data types can be defined with the ABAP Dictionary. These global data types can be use in ABAP
program by TYPE command. The data types of database tables are a subset of all possible types, namely
flat structures. Thus, data type in the ABAP Dictionary is the user's view on the data. ABAP Data Types can
be divided into two categories.
Objects in Data Dictionary
Objects created in the ABAP Dictionary are created in the underlying relational database using these data
definitions. The ABAP dictionary thus describes the logical structure of the object used in the application
development and shows how they are mapped to the underlying relational database in table or view. As
discussed, most important object types in the ABAP dictionary are tables, views, types, domains, search
helps and lock objects.
Tables:
Tables are defined independently of the database. First the table structure is created in the ABAP dictionary
then the table is created in the underlying database from this structure.
Views:
Views combines more than one table. The structure of the view is defined in the ABAP Dictionary. With the
help of views, application-dependent view can be defined that combines the data.
Types:
Types are generally used in ABAP programs and ABAP dictionary to define the structure of the fields,
variables, constants, tables, etc. Types can be further classified as elementary types, reference types or
complex types. Data element, structure and table types are the type categories under user defined data
types.
Domains:
Domain is a central object which defines the technical attribute of a field. Technical attribute refers to data
type, length, fixed value and interval of a field (field of the table, structure, table type etc.). Domain is
assigned to the data element which in turn is assigned to the table fields or structure fields. So all the fields
which use the data element have the technical settings defined by the domain.
Search Helps:
With search help user can display the list of all possible input values for a screen field. Whenever 'F4' key is
pressed on the screen field, popup will appear having the list of entries which satisfies the search in that
screen field. You can select the needed record. There are three types of search help, 'elementary search
helps', 'collective search helps' and 'Append search helps'.
Lock objects:
In R/3 system, multiple users can access same object simultaneously. When one person is editing the
program/transaction, locks are set so that no other person can make changes to that program at the same
time. Function modules are generated automatically from the lock object definition of ABAP Dictionary.
These function modules are responsible to enqueue or dequeue the locks on the objects.
Data Types
Global data types can be defined with the ABAP Dictionary. These global data types can be use in ABAP
program by TYPE command. The data types of database tables are a subset of all possible types, namely
flat structures. Thus, data type in the ABAP Dictionary is the user's view on the data. ABAP Data Types can
be divided into two categories.
- Build-In elementary Data Types
- User-Defined Data Types
Built in Elementary Data Types
There are some Data types which are already defined in ABAP Dictionary. These data types are converted
into their corresponding ABAP Data type, during runtime. Some data types have a predefined length and set
templates for output.
User-Defined Data Types
User defined data types can be defined and stored for all the programs in the ABAP Dictionary. These user
defined data types can be defined either globally in ABAP Dictionary or locally in ABAP programs with
TYPES command. Both the declarations provide the same functionalities which define the user defined types
according to the business and program requirement. The types defined globally in the Data Dictionary can be
accessed by ABAP programs to define data objects.
Elementary Data Types
Elementary types are part of the dual-level domain concept for fields in the ABAP Dictionary. The elementary
type has semantic attribute such as data type, length, texts, value tables, documentation etc.
Elementary types are described by the Data Elements. Data type can be specified in two ways.
By directly assigning to an ABAP dictionary type.
You can directly assign a predefined ABAP Dictionary type and a number of characters to an
elementary type.
Assigning to a domain.
The technical attributes are inherited from the domain. Domain specifies the technical specification of
the data element.
Reference Data Types
Reference types describe the data objects that contain references (pointers) to other objects (data objects
and objects in ABAP Objects). However there exist no predefined references- you have to define them
explicitly. There is a hierarchy of the reference types that describes the hierarchy of objects to which
references can point.
Complex Data Types
Complex types are made up of other types. You can access a complex data types either as a whole or by the
individual component. Complex data types group semantically related data under the single name and
manage and process them. There are no predefined complex data types defined in ABAP. They can either
be defined in ABAP program or in the ABAP Dictionary.
Use Tcode SE11 for Data Dictionary
Lets See the tables inside a cube
Name of cube is "ZICPR1"
In Infocube we will have dimension tables and fact table
we have 6 tables for dimensions
4 for user defined dimensions of cube and 2 for data package and unit.
We have 2 fact tables
E fact table and F fact table
Initially data will be stored in F fact table.. when we compress Request of Infocube,
data will be moved form F fact table to E fact table
Click on display
This is the content of our fact table..
As we know, there wont be any alphabetic characters in fact table..
Note : Know how of Data dictionary is really important for a BI consultant....
Note : Know how of Data dictionary is really important for a BI consultant....
Very useful....
ReplyDeleteThanks