Data Dictionary (DDIC Objects)

ABAP Dictionary:-

(1) Data Base Table :

(2) Views:

(3) Data Types:

(4) Type Group:

(5) Domain:

(6) Search Help:

(7) Lock Object:

(1) Data Base Table :

Transparent Table : It used to store Application data such as Master Data and Transactional Data. we always create transparent table.
There is One to One relationship.

Pooled Table:  Pooled tables are used to store control data (screen sequence, program parameters temporary data etc). The data from several pooled tables can be stored together in a table pool. 
This is many to one relationship i.e for many pooled table in DDIC only one Database table will be created in database table.

Cluster Table :  Cluster tables are logical tables that must be assigned to a table cluster  when they defined. Cluster tables can be used to store control data. They can also be used to store temporary data or texts, such as documentation.

This is many to one relationship i.e for many cluster table in DDIC only one Database table will be created in database table.
All table in the cluster table should have a common primary key.


Append Structure:-    If we want to additional field (Enhancement to add field)  in the standard data base table then we use append structure.

(2) Views:  View are four types: Database View, Projection View, Help view, Maintenance View.

Data base view:  it is a group of table selected some particular field on each table. Join operation is used to combine information for multiple tables.

Projection view: created from single table and suppressing or hiding some field we use projection view.

Help view: We use Help view as selection-method for search help. Help view can be used as selection methods for search helps . it might be necessary to create a help view if you are trying to accomplish an outer-join.

Maintenance view:  these views permit maintenance of data base table . Sm30 and SE54 are provided for working with maintenance view.

(3) Data Types:  Data types are the actual type definitions in the ABAP Dictionary. They allow you to define elementary types, reference types , and complex types that are visible globally in the system. 

Data types are three types: Data Element , Data Structure, Table Type.

Data elements: Data elements in the ABAP Dictionary describe individual fields. Data elements can be elementary types or reference types ( you can use the TYPE addition to refer directly to a data element.).

Data Elements Defined the Semantic attribute of  field.

Data element = Documentation (Short Text) + Domain (Data Type + length)

Advantages: 

       (1) Reusability of Data Type, length , Description.

       (2) To maintain the Relationship between the tables. the related fields from each table should have the  

           common domain.



Further characteristic:-
    Parameter ID:
Set/Get parameter ID
A field can be filled with proposed values from SAP memory using a parameter ID.
Example
A user only has authorization for company code 0001. This company code is stored in memory at the beginning of a transaction under the corresponding parameter ID. Fields that refer to the data element are automatically filled with the value 001 in all subsequent screen templates.
(Example: In table VBAK sales order header parameter ID is AUN for field VBELN (sales order number.)
Dependencies
A field in the screen template is only filled automatically with the value stored under the parameter ID of the data element if this was explicitly permitted in the Screen Painter.

Data structure: Structure is the group of field. Structure  cannot hold the data. When you create a structure in the ABAP Dictionary, each component must have a name and a data type.

We can use the LIKE addition in an ABAP program to refer to a structure in the ABAP Dictionary.

Table Type: Table types are construction blueprints for internal tables that are stored in the ABAP Dictionary. When you create a table type in the ABAP Dictionary, you specify the line type, access type, and key. The line type can be any data type from the ABAP Dictionary, that is, a data element, a structure, a table type, or the type of a database table. You can also enter a predefined Dictionary type directly as the line type, in the same way that you can with a domain.

In an ABAP program, you can use the TYPEaddition to refer directly to a table type.

(4) Type Groups:

we can define data types in type group in the ABAP dictionary instead of defining them within an ABAP program.

Type Group Name has maximum of 5 characters.

Define Like that :

Type-Pool  SLIS.

SLIS is created by SAP to work with all the data type required to work with ALV.

The types in type group must be declared in ABAP program with TYPE-POOLS command to access the data type from the TYPE-GROUP.

(4) Domain:    It use to define the technical attributes (Data type and length) and the value ranges (fixed value and intervals).

Domain is assign to data element.

All the table fields and structure component use this data element and there value range defined by Domain.

Conversion Routine:-

A conversion routine can be assigned to a domain in the ABAP Dictionary.

Conversion takes place when converting the contents of a screen field from display format to SAP-internal format and Sap -internal format to Display format and when outputting with the ABAP statement WRITE, depending on the data type of the field.

If standard conversion is not suitable, it can be overridden by specifying a conversion routine in the underlying domain.

A conversion routine is identified by its five-place name and is stored as a group of two function modules. The function modules have a fixed naming convention. The following function modules are assigned to conversion routine xxxxx:

CONVERSION_EXIT_xxxxx_INPUT (The INPUT module performs the conversion from display format to internal format. )

CONVERSION_EXIT_xxxxx_OUTPUT (The OUTPUT module performs the conversion from internal format to display format.)

If a screen field refers to a domain with a conversion routine, this conversion routine is executed automatically each time an entry is made in this screen field or when values are displayed with this screen field.

(6) Search Help:     Search help is used to find the particular field in easy way by pressing F4. it provides the possible value for the screen field.

Search help are two types Elementary search help and collective search help.

Elementary search help:- we can gets the data from a single table. in selection method we give the table name. Through Import and Export Parameters.

collective search help:- combination of elementary search helps. when we need to fetch data based on multiple selection criteria's from more than one tables then we use collective search help.

ex: search for customer- By General data, By Company code data, By City etc.

( collective search helps has no selection method, it's the combination of two or more elementary search help)

Search help Exit in Collective search help it's the function module with predefined interface, it's the extra code that we can included in processing of the search help at specific time.

(7) Lock Object: lock object is data dictionary object it's use for locking the Database table.

Lock Object's are four types:  

1. Exclusive / Write Lock

2. Shared lock / Read Lock

3. exclusive but not cumulative

4.Optimistic lock.

Exclusive:- The owner of the object can go for display and edit lock. It's not allowed to other user.

Shared Lock:- The owner of the object can edit and display the data of the table, but other user can go for only display not edit mode.

Exclusive but not cumulative:-  exclusive but not cumulative locks can be called only once from the same transaction. Each further lock request will be rejected. owner of the object can display and edit only once it's not allowed more than one time.

Optimistic lock:- Optimistic locks initially behave like shared locks and can be converted into exclusive locks.

We Use two function module.

1. ENQUEUE_EZ(Table-name)     ( like ENQUEUE_EZLFA1  for Locking.)

2. DEQUEUE_EZ(Table-name)      (like DEQUEUE_EZLFA1 for Releasing /Unlocking.)