IBM Cognos User Manual page 30

For more information on creating Cognos Transformer models, see "Creating a
Model" on page 24.
Use List Reports
Data source queries using reports perform most efficiently when the report is a list.
Graphs, dashboards, crosstabs, and complex reports cannot be used as data source
queries.
Importing Dimensional Packages
Use the Insert Dimension from Package command when importing dimensional
packages if you want the dimensional structure maintained. This option preserves
the dimension levels and uses the smallest set of query items.
Importing Time Dimensions from Packages
When you create a query in Cognos Transformer based on a Framework Manager
package that contains hierarchical time-related categories, Cognos Transformer
interprets the time-related categories as a regular dimension and not as a time
dimension. As a result, the time dimension in your PowerCube will not contain
any relative time categories.
To avoid this problem, ensure that you import all of the data needed to define
your time dimension, and use Cognos Transformer to create the date levels and
categories.
Prompts in Report Data Sources
You can use a report with prompts as a data source in Cognos Transformer. You
must provide values for any mandatory prompts "Edit Existing Prompts in IBM
Cognos Reports and Packages" on page 29 when adding a query based on the
report data source to the model. Cognos Transformer asks you for these values
only the first time you add a query from a report data source. Any values you
provide are cached.
If you want to add a second query using the same report as a data source to your
Cognos Transformer model, you will not be prompted to provide values for
mandatory prompts. The values in the cache will be used. Although you can
refresh the source when adding the second query to force Cognos Transformer to
reprompt you for values, data will still be retrieved based on the first query.
To create two queries in your Cognos Transformer model that are based on the
same report data source, where you want to provide different values for
mandatory prompts, you must duplicate the report data source. Use one report
data source to add the first query to the model and use the duplicate report data
source to add the second query to the model.
Extra queries may appear when you import a report that contains prompt pages.
These queries can be identified by the presence of query items named Use Value
and Display Value. Avoid importing query items from these queries.
For more information about prompt support, see "Edit Existing Prompts in IBM
Cognos Reports and Packages" on page 29, and "Using IBM Cognos Reports to
Create a Data Source" on page 193.
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IBM Cognos Transformer Version 10.1.1: User Guide