As a result of modifying a Dimension, you do in fact rebuild the Cube with the most current information, both Metadata and Fact Data, from the underlying relational database—forall Dimensions, not just the one you are modifying.
What, then, is the purpose of Rebuild Cube? For one, it enables you to rebuild the cube without going through the sequence of screens involved in modifying a dimension. The Rebuild Cube also provides you with other options on how to update a cube with data from the underlying source database. Rebuild Cube communicates updates that occur in the source database so that the proCube multidimensional cube contains the most current information.
We will examine the options that the Rebuild Cube feature provides in this topic and the following. In Ramifications of Rebuild Cube Options, a matrix lists the ramifications of the three rebuild types.
When you carry out a “Rebuild Cube” via Xchange, no matter which option you select, you clear all Fact Data (figures) that appears in proCube and then reload the most current Fact Data from the source relational database.
Let’s examine first how to update a cube, via Rebuild Cube, so that it updates Fact Data only.
Before proceeding, consider a proCube data point in the example database as it currently exists.
At the intersection of Ana Trujillo Emparedados y helados and Mozzarella di Giovanni, Drill Through to Relational Source on that data point. You will see that the multidimensional point is composed of a single transactional record.
Figure 1. Sales Order Drill Through - Mozzarella and Ana Trujillo
In order to proceed using the Northwind SQL Server Database for the remainder of this topic, create a new record that also will contribute to this data point. Create a transactional entry that represents an order from the Customer Ana Trujillo Emparedados y helados for a quantity of 15 of the Product Mozzarella di Giovanni.
For this and the following examples, you can create like records in an example database, as indicated; alternatively, you should be able to read on and follow the logic of what is being described, and thereby gain a solid understanding of the Rebuild Cube function.
Having entered a new transaction, you will proceed to use Rebuild Cube so that the procedure brings the exact current Fact Data in the underlying relational system into proCube:
To rebuild the cube:
From the Data ribbon's Xchange Group, click Rebuild Cube to open the Rebuild Cube dialog. The Rebuild Cube dialog opens with the SalesOrder cube and Add Metadata and Refresh Fact Data is selected.
Figure 2. Rebuild Cube - Refresh Factdata Only
Instead select Refresh Fact Data Only as shown in the preceding figure.
This prepares you to re-load the cube with Fact Data from the underlying relational database—no other update will occur. For example, if new Members have been added to the underlying tables they will not appear in the cube. Keep in mind, however, that if you have entered any numbers yourself at data intersection points [and to have done so, you would need to have enabled Multi-Dimensional Editing Allowed in the Cube Properties dialog], those numbers will be replaced with the data as it occurs in the underlying database.
Proceed with the Factdata Only update by clicking OK.
Assuming you still have the example slice open, press F9; the data point will appear as follows:
Figure 3. Slice - Quantity 25
Drill Through to Relational Source on the data point. Now, the multidimensional point is composed of a two transactional order records—the original one and example entry, for 15 units.
Figure 4. Drill Through Shows the New Transaction of 15 Units
In sum, by using Rebuild Cube and selecting Refresh Fact Data Only, you will update your Cube with the most current Fact Data, including Fact Data entries that occurred since the Cube was built or re-built.