Chapter 01 overview of abap dictionary1

Editor's Notes

• #3: In previous versions of SAP (e.g. Version 3.0), ABAP was known as ABAP/4, as it is a 4th Generation language
• #4: A data dictionary is a centralized storage location for information about the data that is stored in a database. This information is often called “metadata” (data about data). A data dictionary provides answers to questions such as: What data is contained in the database? What are the attributes of this data: name, length, format, etc.? What relationships exist among different data objects? SAP’s data dictionary is called the ABAP Dictionary. As an ABAP developer, it is unlikely that you will be responsible for creating and maintaining objects within the ABAP Dictionary. The purpose of this chapter is to familiarise you with how objects are created, stored, and used by the ABAP Dictionary.
• #5: The ABAP Dictionary: Enforces data integrity Manages data definitions without redundancy Is tightly integrated with the rest of the ABAP Workbench
• #6: Enforcing data integrity is the process of ensuring that data entered into the system is logical, complete, and consistent. When data integrity rules are defined in the ABAP Dictionary, the system automatically prevents the entry of invalid data. Defining the data integrity rules at the dictionary level means they only have to be defined once, rather than in each program that accesses that data. The following are examples of data lacking integrity: A date field with a month value of 13 An order assigned to a customer number that doesn’t exist An order not assigned to a customer
• #7: Managing data definitions without redundancy is the process of linking similar information to the same data definition. For example, a customer database is likely to contain a customer’s ID number in several places. The ABAP Dictionary provides the capability of defining the characteristics of a customer ID number in only one place. That central definition then can be used for each instance of a customer ID number.
• #8: The ABAP Dictionary’s integration with the rest of the development environment enables ABAP programs to automatically recognize the names and characteristics of dictionary objects. Additionally, the system provides easy navigation between development objects and dictionary definitions. For example, as a programmer, you can double-click on the name of a dictionary object in your program code, and the system will take you directly to the definition of that object in the ABAP Dictionary. When a dictionary object is changed, a program that references the changed object will automatically reference the new version the next time the program runs. Because ABAP is interpreted, it is not necessary to recompile programs that reference changed dictionary objects.
• #9: The basic objects of the ABAP Dictionary are tables, data elements and domains. Tables are the structures that actually store the information that is in the database (i.e., customer information). Tables are composed of rows (called records) and columns (called fields). Data elements and domains are used to describe the characteristics of fields. More information about these objects will be covered in future chapters.
• #10: The database utility provides the interface between the ABAP Dictionary and the underlying database management system (DBMS). It supports the creation of tables and secondary indices in the database both online and in the background. Whenever you make a change to a dictionary object that affects the underlying database, the database utility is activated. Usually it works silently behind the scenes, but occasionally the database utility will prompt you for information. This occurs when an error is encountered or when existing data must be converted. The database utility provides the interface to the DBMS by automatically generating the Data Definition Language (DDL) that the DBMS understands.