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what is the use of data dictionary

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  • author's profile photo Former Member
    Former Member
    Posted on Jan 30, 2008 at 08:14 AM

    data dictionary holds the metadata ( data about the data) mainly the defenations of global structures, domain, tables, search help, lock object etc.

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  • author's profile photo Former Member
    Former Member
    Posted on Jan 30, 2008 at 08:15 AM

    ashok,

    Just login to r/3 server and enter tcode se11.

    all the 6 elements here are known as data dic objects.

    Viz:-

    database table--to create/change/display database table

    view--create/change/display for view

    data type:-create/change/display data type

    type group:-create/change/display type group

    domain:-create/change/display

    search help:create/change/display search help.

    lock object:- create/change/display lock object

    The most important object types in the ABAP Dictionary are tables, views, types, domains, search helps and lock objects.

    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.

    Different fields having the same technical type can be combined in domains. A domain defines the value range of all table fields and structure components that refer to this domain.

    The ABAP Dictionary also contains the information displayed with the F1 and F4 help for a field in an input template. The documentation about the field is created for a data element that describes the meaning of the contents of a table field. The list of possible input values that appears for the input help is created by a foreign key or a search help.

    Check the links

    http://help.sap.com/saphelp_webas620/helpdata/en/cf/21ea31446011d189700000e8322d00/content.htm

    http://help.sap.com/saphelp_webas620/helpdata/en/cf/21ea43446011d189700000e8322d00/content.htm

    http://help.sap.com/saphelp_webas620/helpdata/en/90/8d72fbb1af11d194f600a0c929b3c3/content.htm

    Don't forget to reward if useful...

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  • author's profile photo Former Member
    Former Member
    Posted on Jan 30, 2008 at 08:16 AM

    Hi,

    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.,

    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

    there is lot more than this about DDIC

    Regards,

    theja.

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  • author's profile photo Former Member
    Former Member
    Posted on Jan 30, 2008 at 08:32 AM

    Hi Sir ,

    Please have a look below .Hope it is suitable and simpler solution for your question.

    Please do reward if useful.

    Thankx.

    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. The data types of database tables are a subset of all possible types, namely flat structures.

    Data Elements

    Data elements in the ABAP Dictionary describe individual fields. They are the smallest indivisible units of the complex types described below, and are used to specify the types of columns in the database. Data elements can be elementary types or reference types.

    Structures

    A structure is a sequence of any other data types from the ABAP Dictionary, that is, data elements, structures, table types, or database tables. When you create a structure in the ABAP Dictionary, each component must have a name and a data type. In an ABAP program, you can use the TYPE addition to refer directly to a structure.

    If you define a local data type in a program by referring to a structure as follows:

    TYPES <t> TYPE <structure>.

    Table Types

    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.

    Type Groups

    Before Release 4.5A, it was not possible to define standalone types in the ABAP Dictionary to which you could refer using a TYPE addition in an ABAP program. It was only possible to refer SAP AG BC - ABAP Programming

    Data Types in the ABAP Dictionary to flat structures. Structures in programs corresponded to the structures of database tables or structures in the ABAP Dictionary. In ABAP programs, you could only refer to database tables and structures in the ABAP Dictionary using LIKE. It was, however, possible to refer to individual components of the Dictionary type. Complex local data types such as internal tables or deep structures had no equivalent in the ABAP Dictionary. The solution to this from Release 3.0 onwards was to use type groups. Type groups were based on the include technique, and allowed you to store any type definitions globally in the Dictionary by defining them using TYPES statements.

    Views:

    There are 4 types views are avilable in SAP.

    Database View - To club more than one table

    Projection View - To hide fields in one table

    Maintanance View - To maintain database records in table

    Help View - To provide help for a fields (Same functionality as Search help. This is outdated)

    View are improves perfromance in the following aspects

    1. If you want to use more than two table in 'JOIN' condition better to use Views . It will improves performance of a program

    2. If you want to use mutiple FOR ALL ENTRIES clause, better to club all SELECT statement in a view.

    Lock Objects:

    Lock objects are use in SAP to avoid the inconsistancy at the time of data is being insert/change into database.

    SAP Provide three type of Lock objects.

    Read Lock(Shared Locked)

    protects read access to an object. The read lock allows other transactions read access but not write access to

    the locked area of the table

    Write Lock(exclusive lock)

    protects write access to an object. The write lock allows other transactions neither read nor write access to

    the locked area of the table.

    Enhanced write lock (exclusive lock without cumulating)

    works like a write lock except that the enhanced write lock also protects from further accesses from the

    same transaction.

    You can create a lock on a object of SAP thorugh transaction SE11 and enter any meaningful name start with EZ Example EZTEST_LOCK.

    Use: you can see in almost all transaction when you are open an object in Change mode SAP could not allow to any other user to open the same object in change mode.

    Example: in HR when we are enter a personal number in master data maintainance screen SAP can't allow to any other user to use same personal number for changes.

    Technicaly:

    When you create a lock object System automatically creat two function module.

    1. ENQUEUE_<Lockobject name>. to insert the object in a queue.

    2. DEQUEUE_<Lockobject name>. To remove the object is being queued through above FM.

    You have to use these function module in your program.

    Search Helps:

    These are two types.

    Elementary n Collective.

    1) Elementary search helps describe a search path. The elementary search help must define where the data of the hit list should be read from (selection method), how the exchange of values between the screen template and selection method is implemented (interface of the search help) and how the online input help should be defined (online behavior of the search help).

    2) Collective search helps combine several elementary search helps. A collective search help thus can offer several alternative search paths.

    3)An elementary search help defines the standard flow of an input help.

    4) A collective search help combines several elementary search helps. The user can thus choose one of several alternative search paths with a collective search help.

    5)A collective search help comprises several elementary search helps. It combines all the search paths that are meaningful for a field.

    6)Both elementary search helps and other search helps can be included in a collective search help. If other collective search helps are contained in a collective search help, they are expanded to the level of the elementary search helps when the input help is called.

    See the below link to understand this completely:

    http://help.sap.com/saphelp_nw2004s/helpdata/en/cf/21ee93446011d189700000e8322d00/frameset.htm

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  • author's profile photo Former Member
    Former Member
    Posted on Jan 30, 2008 at 08:34 AM

    Data definitions (metadata) are created and managed in the ABAP Dictionary. The ABAP Dictionary permits a central description of all the data used in the system without redundancies. New or modified information is automatically provided for all the system components. This ensures data integrity, data consistency and data security.

    You can create the corresponding objects (tables or views) in the underlying relational database using these data definitions. The ABAP Dictionary therefore describes the logical structure of the objects used in application development and shows how they are mapped to the underlying relational database in tables or views.

    The ABAP Dictionary also provides standard functions for editing fields on the screen, for example for assigning a screen field an input help.

    What Information is Stored in the ABAP Dictionary?

    The most important object types in the ABAP Dictionary are tables, views, types, domains, search helps and lock objects.

    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.

    Different fields having the same technical type can be combined in domains. A domain defines the value range of all table fields and structure components that refer to this domain.

    The ABAP Dictionary also contains the information displayed with the F1 and F4 help for a field in an input template. The documentation about the field is created for a data element that describes the meaning of the contents of a table field. The list of possible input values that appears for the input help is created by a foreign key or a search help.

    http://help.sap.com/saphelp_webas610/helpdata/en/cf/21ea31446011d189700000e8322d00/content.htm

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