Data definitions also called as meta data are managed and created in ABAP Dictionary. It allows to maintain a huge volume of data without data redundancy. The ABAP Dictionary describes the logical structure of all the dictionary objects used in Application development. It also provides you with the flexibility of accessing the data on the screen and allows you to maintain manage and create without any programmers intervention.
The data dictionaries can be categorized into the following.
- Database table
- Data types
- Search Help
- Lock Objects
Tables can be defined independently in the database in the ABAP Dictionary. The fields of the table are defined together with their data types and lengths.
A table definition has following components:
A View is a logical representation of tables. This is just a way of organizing the data by combining more than one table by comparing the common fields which is called a join.
It’s an attribute to tell as to what kind of data is it going to hold like numbers, characters, integers etc. A data type can be an elementary data type or a reference data type.
A domain contains the technical attributes of the data type. Like the length, the actual data type ( like char, integer), The output characteristics and the value range which tells us as to what kind of data can be accepted as a valid input.
A search help is simply what you see in SAP when you key in the F4 button. It provides you with the list/range of values.
A search help can be categorised into three types:
Elementary Search help
Collective Search Help
Append Search Help
A lock object is virtual link of an sap table which is used to synchronize the data when more than one user attempts to write to the Database table. These lock objects are called and handled inside the program based on requirement.