Logical tables exist in the Business Model and Mapping layer.
The logical schema defined in each business model must contain at least two logical tables, and you must define relationships between them.
Each logical table has one or more logical columns and one or more logical table sources associated with it. You can change the logical table name, reorder the logical table sources, and configure the logical keys, both primary and foreign.
This section contains the following topics:
If a table does not exist in your physical schema, you need to create the logical table manually.
You create logical tables by dragging and dropping a physical table from the Physical layer to a business model in the Business Model and Mapping layer.
Drag and drop operations are usually the fastest method for creating objects in the Business Model and Mapping layer. If you drag and drop physical tables from the Physical layer to the Business Model and Mapping layer, the columns belonging to the table are also copied. After you drag and drop objects into the Business Model and Mapping layer, you can modify the objects in the logical table without affecting the objects in the Physical layer.
When you drag physical tables, with key and foreign key relationships defined, to a business model, logical keys and joins are created that mirror the keys and joins in the Physical layer. This occurs only if the tables that you drag include the table with the foreign keys. If you create new tables or subsequently drag additional tables from the Physical layer to the Business Model and Mapping layer, the logical mappings between the new or newly dragged tables and the previously dragged tables must be created manually.
See Defining Logical Joins with the Joins Manager and Defining Logical Joins with the Business Model Diagram for more information about joins.
To create a logical table by dragging and dropping:
In the Administration Tool, select one or more table objects in the Physical layer.
You must include the table with the foreign keys if you want to preserve the keys and joins from the Physical layer.
Drag and drop the table objects to a business model in the Business Model and Mapping layer.
When you drop them, the table objects, including the physical source mappings, are created automatically in the Business Model and Mapping layer.
To create a logical table manually:
After creating a logical table manually, you must create all keys and joins manually.
You can add a new logical table source, edit or delete an existing table source, create or change mappings to the table source, and define when to use logical tables sources and how content is aggregated.
See Managing Logical Table Sources (Mappings) for instructions about how to perform these tasks.
You can improve the performance of fragmented logical table sources by enabling the data driven fragment selection option in the
Data driven fragment selection is disabled by default.
To enable data driven fragment selection:
After creating tables in the Business Model and Mapping layer, you specify a primary key for each dimension table.
Logical dimension tables must have a logical primary key. Logical keys can be composed of one or more logical columns.
Note:
Oracle recommends that you do not specify logical keys for logical fact tables.
To specify a primary key in a logical table:
Oracle recommends that you do not use foreign key joins in logical tables.
If you must create these joins, you must first enable the option Allow logical foreign key join creation in the Options dialog.
See Creating Logical Foreign Key Joins with the Joins Manager for more information.
The Foreign Keys tab of the Logical Table dialog exists so that you can view logical foreign keys you might have had in a previous release of Oracle Business Intelligence.