Data Dictionary Tutorial (Lesson -2)

A 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”).
What is Data dictionary used for ?

• Management of data definitions
• Provision of information for evaluations
• Support for software development
• Support for documentation
• Ensuring that data definitions are flexible and up-to-date

Objects in the ABAP Dictionary resided on three levels that support their re-usability. These levels are:

1. Tables and structures
2. Data elements
3. Domains

Lets look into them in detail -

Domains

• Describes the technical characteristics of a table field
• Specifies a value range which describes allowed data values for the fields
• Fields referring to the same domain (via the data elements assigned to them) are changed when a change is made to the domain
• Ensures consistency

Ex. Purchasing document number (EBELN)

Data Elements

• Describes the role played by a field in a technical context
• Fields of same semantic meaning can refer to the same data element
• Contains the field information

Ex. Purchasing document number (EBELN)

Tables

• Represent the Database Tables where data actually resides.
• Tables can be defined independently of the database in the ABAP Dictionary.
• The fields of the table are defined with their (database-independent) SAP ABAP data types and lengths.

Structures

• Are record declarations that do NOT correspond to a Database Table.
• Just like user-defined data type.
• Defined like a table and can then be addressed from ABAP programs.
• Structures contain data only during the runtime of a program.

Aggregated Objects of ABAP Dictionary

Aggregated means consisting of several components. In the ABAP Dictionary, aggregated objects are objects which come from several different transparent tables.

1. Views
2. Search Help
3. Lock Objects

Lets look into them in detail

Views

• Views in SAP _ ABAP are used to summarize data which is distributed among several tables
• The data of a view is not actually physically stored. The data of a view is instead derived from one or more other tables
• It is tailored to the needs of a specific application

Search Help

• A Search help is a tool to help you search for data records in the system
• An efficient and user-friendly search assists users where the key of a record is unknown

Lock Objects

• Simultaneous accessing of the same data record by two users in the SAP system is synchronized by a lock mechanism.
• Locks are set and released by calling certain function modules. These function modules are generated automatically from the definition of so-called lock objects in the ABAP/4 Dictionary

Function modules :
Enqueue_<obj name> – to lock the table
dequeue_<obj name> – to release the lock

Important Transactions

• SE11 : Data Dictionary Initial Screen (SE12 Display only)
• SE13 : ABAP Dictionary : Technical Settings
• SE14 : Database Utility
• SE15 : Repository Information System
• SE16 : Data Browser
• SE17 : General table Display
• SE55 : Table View Maintenance
• SM30 : Table Maintenance