DATA DICTIONARY

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DATA DICTIONARY


DATA DICTIONARY Tables: are defined in the ABAP Dictionary independently of the

database. A table having the same structure is then created from this table definition in the underlying database.

Views: are logical views on more than one table. The structure of the view is defined in the ABAP Dictionary. A view on the database can then be created from this structure.

Types: are used in ABAP programs. The structure of a type can be defined globally in ABAP programs. Changes to a type automatically take effect in all the programs using the type.

Lock Objects: are used to synchronize access to the same data by more than one user. Function modules that can be used in application programs are generated from the definition of a lock object in the ABAP Dictionary.

Search Help: It is tool to help you search for data records in the system.It is an efficient and user-friendly search aid for cases where the key of the record is unknown.


DATA DICTIONARY The ABAP/4 Dictionary describes the logical structure of the objects used in application development and shows how they are mapped to the underlying database in tables or views. Tables, Structures and Views are most important objects of ABAP/4 dictionary.Tables are defined independently of the database.Once these objects are defined and activated they are available to all system components,thus ensuring data integrity,data consistency and data security. The basic objects for defining data in ABAP/4 dictionary are tables,data elements and domains.Domians are used for the technical definition(for example field type,field length),and data elements are used for semantic definition(like description).


DATA DICTIONARY


DATA DICTIONARYFields are not independent objects,they are dependent on tables and therefore can only be maintained within table,they refer to data element.Each data element is dependent on the existence of the domains.The data element is the semantic attribute for field/domain.It describes exactly one role of a domain in a particular business context for its dependent fields.The domain is the central object for defining the technical characteristics of the business object.It describes the value range of the field.This id determined by specifying formal characteristics such as external format,length and so on.Domains can be defined by not any further reference to other dictionary objects.


DATA DICTIONARY In ABAP/4 dictionary relationships can be defined between fields.These relationships are called foreign keys and must be explicitly defined at the first level.Foreign keys are used above all to ensure data consistency.Data entered should be checked against existing data to ensure that there are no contradictions. The table that contains the foreign key is called foreign key table.The table that contains the valid set of values is called the check table.Technical Requirements For Creating a Foreign Key.The check must occur against a field within the primary key of the check table.


The domain name for the foreign key field and the check table field must be same.A generic foreign key is a FK in which one of the PK fields of the check table fields is marked asgenricTRANSPARENT TABLE :

A Transparent table in R/3 has a one to one relationship with a table in the database.It is used to hold application data.The database has the same name. The same no. of fields, and the fields have the same names as the R/3 table definition.Table Pool & Pooled TableA Pooled table has a many-to-one relationship with a database table.It is used to hold system data.The database table has a diff. Name, diff no. of fields, and diff field names than the R/3 table.


Table Clusters & Cluster Tables.

A Cluster table in R/3 has a many to one relationship with a table in the database.

Many cluster tables are stored in a single tables in the database called a table cluster.

Table clusters contain fewer tables than table pools and unlike table pools, the primary key of each table within the table cluster begins with the same field or fields.

When you look at a pooled/ cluster table in R/3, you see a description of a table. However, in the databese, it is stored along with other tables in a single table.


DATA DICTIONARY


DATA DICTIONARY

In addition to tables,structures can also be defined in the DataDictionary.A structure is a series of fields grouped together under a common name.The difference between a table and a structure are:A structure does not have an associated database table.A structure does not have a primary key.A structure does not have technical attributes.You cannot have a structure and a table with the same name.The procedure for creating the structure is same as defining thetable.The only differences are:


DATA DICTIONARY Instead of the tables radio button ,select the Structure radio button.The delivery class and Tab.Maint.Allowed fields do not appear.Structures do not have a primary key.No technical attributes can be specified,such as the data class,size category.A structure can contain another structure.The chain of structures created by including one structure within another structure is called an include structure.The maximum nesting depth is nine.You can include the same structure multiple times within a table if instead of .INCLUDE,you use .INCLU-XXX.


DATA DICTIONARY

The XXX represents your choice of three characters.The three characters will be appended to each field name that is included to make it unique. Special Table fieldsCurrency fields- The numeric amount field is called the currency field of type CURR and the other field is called the currency key field of type CUKY. The currency key is reference field for the CUKY field.Quantity fields It is a field that contains a numeric measurement of type QUAN. It must be linked with to a field of type UNIT. The UNIT field is the reference field for the QUAN field.


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DATA DICTIONARY

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