What is Data 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").
ABAP Dictionary 3 levels
Objects in the ABAP Dictionary resided on three levels that support their re-usability. These levels are:
- Tables and structures
- Data elements
- 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.
- Views
- Search Help
- 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
