The Type 3 Dimension mapping filters source rows based on user-defined comparisons and inserts only those found to be new dimensions to the target. Rows containing changes to the existing dimensions are updated in the target. When updating an existing dimension, the Integration Service saves existing data in different columns of the same row and replaces the existing data with the updates. The Integration Service optionally enters the system date as a timestamp for each row it inserts or updates. In the Type 3 Dimension target, each dimension contains current dimension data.

Use the Type 3 Dimension mapping to update a slowly changing dimensions table when you want to keep only current and previous versions of column data in the table. Both versions of the specified column or columns are saved in the same row.

When you use this option, the Designer creates additional fields in the target:

For example, you might have a site dimension table with store code, location, and overhead that you update after the company changes the location of a store. This dimension is used for sales and overhead calculations. In this case, you need only the more recent two versions of the location information to track the changes and do the calculations. You do not need to know the complete history of all previous locations. With the Type 3 Dimension mapping, you can keep current data and the previous data without having a complete history.