Chapter 6 Working with PDMs

Rebuilding Cubes

The Rebuild Cubes feature allows you to create cubes and dimensions from fact and dimension tables and views. Tables and views support multidimensional types, in this section both are referred to as fact and dimension tables

Once the fact and dimension tables of the data warehouse schema are designed, you can use this information to build the multidimensional cubes. The Rebuild Cubes feature allows the switch to the multidimensional environment by transforming fact tables or views into cubes, and dimension tables or views into dimensions. You can then design the cubes taking into account the different analysis axis of the dimensions. These cubes will serve to generate the text files used to create and populate the OLAP engine.

The Rebuild Cubes feature works only if the tables have a multidimensional type (Fact or Dimension). If the tables have no type, an error message appears.

You define the type of a table or view using the following methods:

Using the Dimensional Type dropdown listbox from the object property sheet

For more information on using the table property sheet, see section Defining tables in chapter Building Physical Diagrams.
Using the retrieve multidimensional objects feature

For more information on retrieving multidimensional objects, see section Retrieving Multidimensional Objects.

Object transformation

The rebuild cubes operation creates multidimensional objects in a multidimensional diagram. If there is no multidimensional diagram in the model when you start the rebuild cubes, it will be created. Otherwise the symbols appear in the active multidimensional diagram or the first multidimensional diagram created in the model.

The rebuild cubes functionality modifies objects according to the following rule:

Physical object	After rebuild cubes, creates
Fact table	One fact with the same name as the fact table + One Cube
Column in a Fact table (except foreign keys)	Measure
Dimensions tables attached to the fact table	One dimension, the name of the dimension corresponds to the concatenation of the dimension tables along the path to the child table, from the furthest to the closest + One hierarchy that becomes the default hierarchy. This hierarchy contains the attributes corresponding to the primary key columns of the tables converted into a dimension
Column in a Dimension table (except foreign keys)	One attribute, the name of the attribute is the concatenation of the dimension table name and column name if column names are ambiguous. Otherwise the name is identical to the name of the column.
References between a fact and a dimension table	One cube dimension association

The Cube Rebuild dialog box allows you to select among the following rebuild modes:

Rebuild mode	Impact
Delete and Rebuild	All objects previously rebuilt are deleted when you start the current cube rebuild
Preserve	Objects previously rebuilt are preserved during current cube rebuild

To start the cube rebuild:

Select Tools→Multidimension→Rebuild Cubes.

The Cube Rebuild dialog box appears.

Select the rebuild mode in the General tab.

Select the fact tables that will be transformed in the Selection tab.

Click OK.

A message in the Output window informs you that the rebuild is successful. The cube and dimension are created and displayed in a multidimensional diagram. You can double-click the diagram node in the Browser to display the symbols of the multidimensional objects.