Domain

A domain describes the technical attributes of a field, such as the data type or the number of positions in a field. The domain defines primarily a value range describing the valid data values for the fields referring to this domain.
We can define following thing in domain- 

    In Definition Tab 
       1. Data Type 
       2. No. Of Characters 
       3. Decimals 
       4. Output length 
       5. Conversion Routine 
       6. Sign (a check box) 
       7. Lowercase (a check box) 


    In Value Range Tab 
       1. F4 Help fixed Ranges        2. Value Table  


The figure below defines the re usability  of domain :

Database Table

Database Table

It helps in create and maintain the tables, table should begin with letter Y or Z and length up to 16 characters.

Tables are defined in the ABAP Dictionary independently of the database. From this table definition follows the creation of the table with the same structure in the underlying database.

Internal Table

An Internal table is a temporary table gets created in the memory of application server during program execution and gets destroyed once the program ends. It is used to hold data temporarily or manipulate the data. It contains one or more rows with same structure.

Transparent Tables

It contains a single table, used to store master data.

It has one to one relationship with a table in database.

For each transparent table there is one associated table in database.

Pool Tables

They are used to hold a large no. of very small table(stores customise and system data).

It has many to one relationship with a table in database.

It is stored in other pool table in a single table called table pool.

Cluster Tables

They are used to hold data from few no. of large tables(stores system data).

It has many to one relationship with table in the database called a table cluster.

It contain less table than table pools.

Table

Classification of Tables:-

                                           

Main Objects of ABAP Dictionary.

ABAP Dictionary is one the best tool of ABAP workbench and it is a central repository for data definitions in SAP system. It is used to store the data definitions, create and maintain user defined types.

ABAP Dictionary provides various tools to edit the SAP screen fields like assigning a field to input help (f4).

ABAP dictionary is a central storage area for the description where we can create the objects and changing, deleting the objects related to data base. The main object type of ABAP dictionary are-

1. Database tables
2. View
3. Data types
4. Type groups
5. Search Help
6. Domains and
7. Lock objects.

Database tables: – It helps in create and maintain the tables, table should begin with letter Y or Z and length up to 16 characters.

View : – It act as virtual table and helps in retrieve the data.

Data type: – It helps in creating the user defined data elements, structure and tables.

Type group: – It creates the data group types in dictionary

Search help: – It defines the search help (F4) for the fields of database table and helps in providing the values for a user search queries

Domains: – Domain specifies the technical characters of a field such as data type field and length.

Lock objects : – It is used to synchronize the same data by one user or multiple users. SAP provides three types of lock objects- Read lock, write lock, enhanced lock.

                                               

ABAP Dictionary

ABAP - It stands for Advance Business Application Programming, it is a SAP based programming language used for SAP applications.

ABAP Dictionary - Data Dictionary is a central source of information for the data in a information management system. Its main function is to support the creation and management of data definitions (or "metadata").
     The ABAP Dictionary permits a central description of all the data used in the system without redundancies. New or modified information is automatically provided for all the system components. This ensures data integrity, data consistency and data security.

The ABAP Dictionary is completely integrated in the ABAP Workbench. The SAP system works interpretatively, permitting the ABAP Dictionary to be actively integrated in the development environment. Instead of the original objects, the interpreters see only internal representations of these objects.

These internal representations are adjusted automatically when the system finds that changes have been made in the ABAP Dictionary. This ensures that the screen and ABAP interpreters, input help, database interface, and development tools always access current data.When you work on development projects, objects of the ABAP Dictionary can be changed any number of times before being activated and made available to the operative components of the system. Objects can have both an active and an inactive version in the ABAP Dictionary at the same time.

Inactive ABAP Dictionary objects have no effect on the runtime system (ABAP processor, database interface). This permits greater changes to several objects without impairing the executability of the system. The objects can be activated together only when they all have been changed.