Create Cubes With External Rollups - IBM Cognos User Manual

Procedure
1. Open the Measure property sheet and click the Rollup tab.
2. In the Regular rollup box, select a rollup function.
3. Click OK.

Create Cubes with External Rollups

In Cognos Transformer, you use the rollup function to summarize measure values
in the cube. If you have specific data that you do not want changed within the
cube, you can use externally rolled up measures to maintain control over which
values are stored and displayed.
Externally rolled up measures can be used with alternate drill-down paths, special
categories, and partitioned cubes, including those partitioned on the time
dimension.
To create a cube with externally rolled up measures, you must first create a
structural query to populate the dimensions, and then create a transactional query
marked for external rollup to set the rollup values. Finally, you specify the Degree
of detail for allocations, if applicable.
Each data record in an externally rolled up transactional data source uses a
category code to reference the category in the model. To avoid ambiguity and
unpredictable results, ensure that each code uniquely identifies a specific category
in the source file. Otherwise, Cognos Transformer makes the code unique by
adding a tilde (~) character with a numeric suffix, creating a blended expression
that cannot be interpreted by other IBM Cognos components.
For example, suppose your cube contains more than one instance of the category
code Item, and so renames the second instance Item~1, the third instance Item~2,
and so on. These category codes are numbered as they are encountered in the
model. This means that the codes do not stay the same, in a predictable sequence,
as your organization (and model) evolves. The tilde characters are interpreted as
non-numeric and, because these codes do not appear in the data source, they are
ignored during the consolidation pass. As a result, duplicate records are
overridden and not summed, despite what may be reported in the log file.
To avoid such problems, use one of the following strategies to make these codes
unique:
v Ensure that all source values are unique in a dimension.
v Create a calculated column in Cognos Transformer, to make your categories
v Edit the .mdl model file to make the category codes unique.
For each special category that has more than one child category, you must provide
the externally rolled up value. Otherwise, the special category value will be
102
IBM Cognos Transformer Version 10.1.1: User Guide
If you select the Average function, you can weight the average by selecting a
measure from the Regular weight box. However, the weighting measure must
have a rollup type of Default (Sum) or Sum.
unique.
For more information about using the Model Definition Language (MDL), see
the Cognos Transformer Developer Guide.