ABAP Dictionary used to create and manage data definitions (metadata). The ABAP Dictionary allows a central description of all the data used in the system. New or modified information is automatically provided for all the system components. Data Dictionary ensures data integrity, data consistency and data security.

The ABAP Dictionary supports the definition of user-defined types (data elements, structures, and table types). We can create the corresponding objects (tables or views) in the relational database using these data definitions. The ABAP Dictionary describes the logical structure of the objects used in application development and shows how they are mapped to the relational database in tables or views.

The ABAP Dictionary describes the logical structure of the objects used in application development and shows how they are mapped to the relational database in tables or views.

The following information is useful and can directly access from the Data dictionary -

• Information on fields displayed with F1 help
• Possible entries for fields displayed with F4 help
• Match code and help views search utilities

Central information repository for application and system data. The ABAP Dictionary contains data definitions (metadata) that allow us to describe all the data structures in the system (like tables, views, and data types) in one place. This eliminates redundancy.

The different types of data dictionary objects are -

• Tables
• Views
• Domain
• Data Element
• Type Groups
• Search Helps/Match code Objects
• Lock Objects
• Structures
• Table Types

• Tables
• Domains
• Data elements
• Structures
• Type Groups
• Table Types

• Views
• Match codes
• Lock objects

The most important features of ABAP/4 dictionary are -

• Integrated to ABAP/4 Development Workbench
• Active in the runtime environment

There are 4 Types of Tables in ABAP dictionary -

• Transparent tables - Exists with the same structure both in dictionary as well as in database exactly with the same data and fields. Both Open SQL and Native SQL can be used.
• Pool tables - Pooled tables in the dictionary has a many-to-one relation with the table in database. Table in the database has the different name as in the dictionary. Pooled table are stored in table pool at the database level.
• Cluster tables - These are logical tables that are arranged as records of transparent tables. One cannot use Native SQL on these tables (only Open SQL). They are not manageable directly using database system tools.
• Internal tables - Internal table is a temporary table stored in the RAM of the application server. It gets created during the program execution and gets deleted once the program ends.

All local objects are not reusable.

Steps to create a table -

• Creating domains (data type, field length, Range).
• Creating data elements (properties and type for a table field).
• Creating tables (SE11).

No, Transparent table do exist with the same structure both in the dictionary as well as in the database. And also exactly with the same data and fields.

ABAP Editor is a tool in the ABAP Workbench in which we enter the source code of ABAP programs and check their syntax. We can also navigate from the ABAP Editor to the other tools in the ABAP Workbench.

We can specify the extent sizes and the tablespace (physical storage area in the database) for a transparent table by setting the size category and data class.

The correction system manages the changes to internal system components such as objects of the ABAP/4 Dictionary.

The functions performed by the data dictionary in a data management system are -

• Management of data definitions.
• Provision of information for evaluation.
• Support for software development.
• Support form documentation.
• Ensures the data definitions are flexible and up to date.

The table attributes define who is responsible for maintaining a table and which types of access can access data.
The most important table attributes are -

• Delivery class
• Table maintenance
• Activation type.

The delivery class controls the degree to which the SAP user or the customer is responsible for table maintenance.
It also -

• Determines whether SAP provides the table with or without contents.
• Determines the table type.
• Determines how the table behaves when it is first installed, at upgrade, when it is transported, and when a client copy is performed.

The difference between table and structure are -

In ABAP, the group of programs into modular units using modularization called as logical blocks. It helps in increasing the program readability and redundancy in process of creating it and during the maintenance cycle. It also helps in reusing the code again.
ABAP data dictionary is used to define the logical structure of objects in the development of application and mapping to the relational database in tables and views.

Some of the objects that constitute data dictionary are as follows - tables, domain, views, data element, search helps or match code objects, type groups, look objects, table types, structure.

Domain - Domain is a central object for explaining the technical characteristics of an attribute of a business objects. It describes the value range of the field.
Data Element – Data element is used to describe the semantic definition of the table fields like description the field. Data element describes how a field can be displayed to end-user.

A data class is a class that contains only fields and crude methods for accessing other classes. Data classes are classified into four types depending on the type of data they contain -

• Master Data: Data change very rarely.
• Transaction Data: Data changes are depending on requirements.
• Organization Data: Data is a customized and entered to the system when the system is configured. It is rarely changed.
• System Data: Data is used by the SAP R/3 system.

The Size category describes the possible space requirement for the table in the database.

Match Code is a tool to help us to search for data records in the system. Match codes are an efficient and user-friendly search tool where key of a record is unknown.

A domain describes the technical settings of a table field. A domain defines a value range, that sets the allowable values for the fields that are referring to this domain. A single domain can be used as origin for any number of fields that are identical in structure.

Delivery class to control the transport of table data for an installation, upgrade, or client copy and transports between customer systems. The delivery class is also used in the extended table maintenance.

Database table.

A match code can be built in two different ways -

• Logical structure - The matchcode data is setup temporarily when the match code is accessed. (Update type I, K).
• Physical structure - The match code data is physically stored in a separate table in the database. (Update type A, S, P).

Repository Info. Systems is a tool that makes data stored in the ABAP/4 Dictionary available.