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Saturday, May 10, 2008

What is Logical Database?Logical database in ABAP programming

The Logical Database Builder then saves you work by using components that you have already defined to generate proposals for other components. Some of the most important attributes of a logical database are set when you define its structure. When you have defined the structure, the Logical Database Builder automatically generates a proposal for the selection include. The system then generates an input mask for the database program, based on the structure of the logical database and the selections.
These generated proposals allow you to create a working logical database quickly. However, you must program refinements such as authorization checks and performance optimization yourself.
• Database tables. The table must be active in the ABAP Dictionary. Tables always have a flat structure. The name of the node must correspond with the name of the table.
• Data types from the ABAP Dictionary: The node may refer to any data type in the ABAP Dictionary. The node name and the name of the data type do not have to be the same. You can use deep data types as nodes.
• Data types from type groups: The node can also refer to a data type from a type group in the ABAP Dictionary. Enter the name of the type group in the corresponding field. You must choose Other types before specifying this type. Data types in type groups were the forerunners of real data types in the ABAP Dictionary. Wherever possible, you should use ABAP Dictionary data types. They have all of the semantic properties of their underlying data elements. This is useful, for example, when you use a logical database to create ABAP Queries.

You edit logical databases using the Logical Database Builder in the ABAP Workbench. To start the Logical Database Builder, use Transaction SE36 or SLDB, or choose Tools ® ABAP Workbench, followed by Development ® Programming environment ® Logical Database Builder. You can also start it by forward navigation from the Repository Browser or other ABAP Workbench tools.
In the Logical database field, you can enter a name of up to 20 characters. The name may also contain a three to ten-character namespace prefix, enclosed in forward slashes.
On the initial screen, you can create, copy, and delete logical databases. However, you can only delete a logical database if it is not linked to an executable program. Even if a logical database is not linked to any executable programs, it can still be used by a program that calls it using the function module LDB_PROCESS. Before deleting one, you should therefore check that it is not still in use. However, the Where-used list function only shows where a logical database is assigned to an executable program.

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