Use Multiple Data Sources

By using multiple data sources for your model, you can reduce the total volume of data processed and thereby shorten processing times in Cognos® Transformer. If used in combination with calculated columns, multiple data sources can minimize or eliminate the need to create database table joins in an external data access tool. Using multiple data sources also enables measure allocation.

For example, suppose your product, customer, and order data is stored in a set of tables. If you were to use this data from a single source, you would need separate tables for Product, Customer, CustomerSite, Order, and OrderDetail. This source would contain many duplicate values, and the joins between the tables would be relatively complex.

Instead, you create three separate sources for Products, Customer/Site, and Order/Order Detail data. The volume of data contained in each is less than that in the single source, and there are only simple joins between Customer and CustomerSite tables, and Order and OrderDetail.

Remember that each source must contain sufficient data to establish context within the dimension map. You cannot perform database table joins in Cognos Transformer.


  1. Using a data access tool such as IBM® Cognos Impromptu or Framework Manager, create each of the data sources required for your model.
  2. From the Welcome page, click Create a new model to use the New Model wizard to add the largest structural data source to your model.

    Tip: If you are already in Cognos Transformer, click New from the File menu.

  3. From the Edit menu, click Insert Data Source and add the additional structural data sources to the Data Sources list.
  4. Repeat to add the transactional data sources to the Data Sources list.