Query Performance Tuning - Expert Cube Development with SSAS Multidimensional Models - page 215

The following screenshot shows the Review Aggregation Usage step of the
Aggregation Design Wizard :

The AggregationUsage property controls how dimension attributes are treated in
the aggregation design process. The property can be set to the following values:

• Full : This means that the attribute or an attribute at a lower granularity

directly related to it by an attribute relationship will be included in every
single aggregation the wizard builds. We recommend that you use this
value sparingly, for at most one or two attributes in your cube because it can
significantly reduce the number of aggregations that get built. You should set
it for attributes that will almost always get used in queries. For example, if the
vast majority of your queries are at the month granularity it makes sense that all
of your aggregations include the Month attribute from your Time dimension.

• None : This means that the attribute will not be included in any

aggregation that the wizard designs. Don't be afraid of using this value
for any attributes that you don't think will be used often in your queries;
it can be a useful way of ensuring that the attributes that are used often get
good aggregation coverage.