Aggregation Design and Usage-Based Optimization - Microsoft SQL Server 2008 Analysis Services - page 423

the wizard, it won't ask you to supply an estimated count of members. If you designed
your aggregations using a smaller (development) version of the database, it makes sense to
reset the estimated counts. When you run the Aggregation Design Wizard on the produc-
tion version of the database, the wizard will get better estimates.

Nonaggregatable Attributes
Some dimension attributes can't be aggregated; that is, they are nonaggregatable . For
example, you wouldn't want to aggregate currencies across the Currency Code attribute.
At any point in time, only a single currency is valid. In aggregation design, such an
attribute needs to participate in all the aggregations in the measure group.

Set the IsAggregatable property of the attribute to FALSE to instruct the aggregation
design algorithm to include this attribute in all the aggregations it designs.

NOTE
Change the IsAggregatable property with care, because setting it to FALSE will affect
all the default members. In addition, we don't recommend that you have more than one
nonaggregatable attribute in a dimension.

Dimension and Attribute Properties
The Cube Dimension Attribute object has an AggregationUsage property that is taken
into account by the aggregation design algorithm when it designs aggregations. Table 23.1
lists the values this property takes.

TABLE 23.1 AggregationUsage Values
Name

Description

The attribute will be inserted into any aggregation designed by the aggre-
gation design algorithm.

Full

The attribute won't be considered by the aggregation design algorithm at all. None

The aggregation design algorithm will always consider this attribute as a
potential candidate.

Unrestricted

The default value for the Cube attribute. If a dimension attribute has no
user-defined hierarchy, none of the attributes in the dimension is consid-
ered at all by the aggregation design algorithm. If the Cube attribute is
part of a user-defined hierarchy, this value is treated as Unrestricted .

Default

Query Usage Statistics

In addition to the ability to design aggregations based on only the structure of dimensions
and attributes, Analysis Services enables you to take into account statistical information
about queries when you design aggregations.