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data dictionary

explain me data class,view and data dictionary

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    author's profile photo Former Member
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    Posted on May 30, 2008 at 05:11 AM

    Hi,

    Dataclass:The data class determines the tablespace in which a table is created

    View:A view is a "virtual table" containing data, which are really stored in one or more other tables. The contents of the View are dynamically generated when called from a program.

    Data dictianary is used to create and store objects.

    Rewardeful.

    Regards,

    Swetha.

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  • author's profile photo Former Member
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    Posted on May 30, 2008 at 05:12 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

    Regards,

    Santosh

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  • author's profile photo Former Member
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    Posted on May 30, 2008 at 05:13 AM

    Hi,

    View:

    In the language of relational databases, a view is a virtual table, that is, a table that is not actually physically stored, instead being derived from one or more other tables.

    In the simplest case, this derivation process can involve simply suppressing the display of one or more fields from a base table (Projection) or transferring only certain records from a base table to the view (Selection). More complicated views can be assembled from several base tables, with individual tables being linked using the relational Join operation.

    The way views are defined in relational database systems, it is possible to use any desired combination of the three fundamental operations - projection, selection, and join - with the single constraint being that only views derived from a single base table, i.e. without applying the join operation, may be relationally operated on in turn.

    data Class : It deramines which space the table is stored.

    data Dictonary : All the tables and releated objects maintaind.

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  • author's profile photo Former Member
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    Posted on May 30, 2008 at 05:14 AM

    Hi,

    Dataclass is the space where table is store in database.

    APPL0 Master data

    APPL1 Transaction data

    APPL2 Organizational and customizing data

    Data dictionary describes the logical structures of the objects used in application development and shows how they are mapped to the underlying relational database in tables/views.

    Data dictionary holds the data definations or metadata. Ex: table defination, type defination etc.

    Check this link for more details.

    http://help.sap.com/saphelp_nw04/helpdata/en/cf/21ea31446011d189700000e8322d00/content.h

    View is a combination of tables and structure is a data type.

    http://help.sap.com/saphelp_erp2005/helpdata/EN/cf/21ecf9446011d189700000e8322d00/frameset.htm

    Regarsd

    Kiran Sure

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  • author's profile photo Former Member
    Former Member
    Posted on May 30, 2008 at 05:15 AM

    hI,

    Dataclass:The data class determines the tablespace in which a table is created

    Data dictianary is used to create and store objects.

    View:A view is a "virtual table" containing data, which are really stored in one or more other tables. The contents of the View are dynamically generated when called from a program or at the runtime it wil have data (Like a RAM in our PC's)

    With RGds,

    S.BArani

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  • author's profile photo Former Member
    Former Member
    Posted on May 30, 2008 at 05:17 AM

    hi there...

    a lot of useful info s available at the following link...

    http://www.sapdb.info/abap-data-dictionary/

    i hope it is helpful to u.

    do reward if it is....

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  • author's profile photo Former Member
    Former Member
    Posted on May 30, 2008 at 05:21 AM

    Hi,

    Views

    Data about an application object is often distributed on several tables. By defining a view, you can define an application-dependent view that combines this data. The structure of such a view is defined by specifying the tables and fields used in the view. Fields that are not required can be hidden, thereby minimizing interfaces. A view can be used in ABAP programs for data selection.

    Database Views

    Data about an application object is often distributed on several database tables. A database view provides an application-specific view on such distributed data.

    Database views are defined in the ABAP Dictionary. A database view is automatically created in the underlying database when it is activated.

    Application programs can access the data of a database view using the database interface. You can access the data in ABAP programs with both OPEN SQL and NATIVE SQL. However, the data is actually selected in the database. Since the join operation is executed in the database in this case, you can minimize the number of database accesses in this way. Database views implement an inner join (see Inner and Outer Join).

    Projection Views

    Projection views are used to hide fields of a table. This can minimize interfaces; for example when you access the database, you only read and write the field contents actually needed.

    A projection view contains exactly one table. You cannot define selection conditions for projection views.

    There is no corresponding object in the database for a projection view. Access to a projection view is mapped by the SAP System onto the corresponding access to its base table. It is also possible to access pooled tables or cluster tables with a projection view.

    Help Views

    You have to create a help view if a view with outer join is needed as selection method of a search help.

    The selection method of a search help is either a table or a view. If you have to select data from several tables for the search help, you should generally use a database view as selection method. However, a database view always implements an inner join. If you need a view with outer join for the data selection, you have to use a help view as selection method.

    Maintenance Views

    Maintenance views offer easy ways to maintain complex application objects.

    Data distributed on several tables often forms a logical unit, for example an application object, for the user. You want to be able to display, modify and create the data of such an application object together. Normally the user is not interested in the technical implementation of the application object, that is in the distribution of the data on several tables.

    A maintenance view permits you to maintain the data of an application object together. The data is automatically distributed in the underlying database tables. The maintenance status determines which accesses to the data of the underlying tables are possible with the maintenance view.

    All the tables in a maintenance view must be linked with foreign keys, that is the join conditions for maintenance views are always derived from the foreign key (see Foreign Key Relationship and Join Condition). You cannot directly enter the join conditions as for database views.

    There are some restrictions for the attributes of the foreign keys with which the tables in a maintenance view can be linked (see Restrictions for Maintenance and Help Views).

    Reward If Helpfull,

    Naresh.

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