The SAP Data Dictionary is an essential part of the SAP system. It helps define and manage data structures. It ensures consistency and integrity of data across the system. Let us look at its main components in detail.
Tables in SAP Data Dictionary
Tables store data in a structured format. Each table consists of rows and columns. SAP tables are classified into three types:
Transparent tables: Store application data and map directly to the database.
Clustered tables: Group multiple tables to store related data efficiently.
Pooled tables: Used to store small, technical data in a common table.
Primary key
The primary key is a unique identifier for each record in a table. It ensures that no duplicate records exist. A table must have at least one primary key. It is often a combination of multiple fields.
Foreign Key
A foreign key links two tables together. It ensures referential integrity between tables. The foreign key field in one table refers to the primary key of another table. This prevents invalid data entry.
Check Table
The check table defines valid entries for the foreign key field. It restricts data input to predefined values. For example, if the sales order table contains customer IDs, the check table ensures that only existing customer IDs are entered.
Value Table
The value table stores possible values ​​for a domain. It is linked at the domain level rather than the field level. Unlike check tables, value tables indicate possible values ​​but do not impose restrictions.
Structure Enhancement in Data Dictionary
Sometimes, we need to enhance an existing SAP table. This can be done using the following:
Append Structure: Adds new fields to a standard SAP table without modifying the original table.
Insert Structure: Inserts predefined structures into a table for reuse.
These enhancements help to customize SAP without affecting the standard functionalities.
Views in SAP
A view combines data from multiple tables. They do not store data but display it in a meaningful way. There are different types of views in data dictionary:
Database Views: Created at the database level and used for performance optimization.
Projection Views: Display selected fields from a single table.
Help Views: Used in search help to display relevant data.
Maintenance Views: Allow data modification from multiple related tables.
Data Types in SAP
SAP ABAP (Advanced Business Application Programming) provides various data types to handle and structure data efficiently. Among them, Data Elements, Structures, and Table Types are widely used in ABAP Dictionary for defining and organizing data
Data Elements: A Data Element is a fundamental data type in SAP ABAP that describes the technical and semantic meaning of a field. It is used to define the type and length of table fields, structure components, and screen fields.
Structures: A Structure is a collection of fields grouped together under a single name. Unlike tables, structures do not store data permanently; they are used to define layouts for processing data in programs, screens, or interfaces.
Table Types: A Table Type defines the structure of an internal table, which is used for temporary data storage and processing within an ABAP program.
Type group
Type group is a collection of related data types. It helps in reusing predefined types in different programs. It is created using TYPE-POOL keyword in ABAP.
Domain
Domain defines the technical characteristics of the field. It includes data type, length and value range. Multiple fields can use the same domain. This ensures consistency of data across tables.
Search help
Search help provides a user-friendly way of searching data. It acts as an input help. SAP provides different types of search helps in data dictionary:
Elementry search help: Retrieves data from a single table.
Collective search help: Combines multiple elementry search helps.
Users can easily select values ​​instead of entering them manually.
Lock objects
Lock objects in SAP ABAP are used to ensure data consistency and prevent simultaneous updates by multiple users. SAP uses enqueue and dequeue mechanisms to manage locks efficiently in data dictionary.
Shared lock: A shared allows multiple users to read the same data simultaneously, but no one can modify it until the shared lock is released.
Exclusive lock: A exclusive lock ensures that only one user can read and modify the data at a time, preventing concurrent updates.
Exclusive but Not Cumulative Lock: This lock type is similar to a shared lock, but it does not allow the same user to request the same lock multiple times. If the user tries to acquire the lock again, the system rejects it.
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