What is data dicionary

Question

i want to know what is mean by domain , data element and data types?

Answer 1

Dictionary
The ABAP/4 Data Dictionary is the central component of ABAP/4 Repository.
It is centralised and structured source of information for business applications
It is the source of every every definition with in R/3 system.
It is totally integrated with other tools of Dev. environment like Screen painter etc.,
Some of the main available functions in the ABAP/4 Dict.
Management of data definitions (Select, Insert, Update and Delete)
Preserve data integrity.
Information about the defined relationship between two tables or even dictionary tells whether table is active or empty.
Dictionary Objects
Tables
Structures
View
Data element
Domain
Lock Objects and
Search Helps
check these sites:
http://sapabap.iespana.es/sapabap/manuales/learnabap/
http://help.sap.com/saphelp_nw2004s/helpdata/en/43/41341147041806e10000000a1553f6/frameset.htm
http://help.sap.com/saphelp_nw04/helpdata/en/cf/21eb6e446011d189700000e8322d00/content.htm
http://help.sap.com/saphelp_nw2004s/helpdata/en/cf/21ea31446011d189700000e8322d00/frameset.htm
http://help.sap.com/printdocu/core/Print46c/en/data/pdf/BCDWBDIC/BCDWBDIC.
http://cma.zdnet.com/book/abap/ch03/ch03.htm
domain
A table is composed of fields. To create a field you need a data element.A data element's definition requires a domain.
The domain contains the technical characteristics of a field, such as the field length and data type.
When you create a new field, you must decide whether to create a new domain or reuse an existing one. To make this decision, determine whether the data type or length of your field should be dependent on an existing SAP field. If your field should be independent, create a new domain. If your field should be dependent, reuse an existing SAP domain. Similarly, you should reuse data elements if your field labels and documentation should change when SAP changes theirs.
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Data element provides business context. i.e., it provides field labels for the field in the backend,
Data type :
A data element is an elementary type. It describes the type attributes (data type, field length and possibly the number of decimal places) and screen information (explanatory text or field help) about unstructured data objects (table fields and structure fields or variables).
Table fields and structure fields with the same contents should refer to the same data element. This ensures that the attributes of these fields are always consistent.
A data element can be referenced in ABAP programs with TYPE. This permits you to define variables that take on the type attributes of the data element in an ABAP program.
Domain :
A domain describes the technical attributes of a field, such as the data type or the number of positions in a field. The domain defines primarily a value range describing the valid data values for the fields referring to this domain.
Different technical fields of the same type can be combined in a domain. Fields referring to the same domain are changed at the same time when a domain is changed. This ensures the consistency of these fields.
Additional info about data element
1.Data type, number of places and possibly the decimal places were entered directly. In this case the field is not filled.
2.A data element is assigned to the field. The field then gets its data type, length and possibly decimal places from this data element. The semantic attributes of the element (field help, representation of the field in input templates with keyword text, column headers for list output of the table contents and editing of the output with parameter IDs) are also copied.