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Chapter 53: Building Multidimensional Cubes in Analysis Services with MDX
53
and Unrestricted — considers this attribute for inclusion in the design without
restrictions.■ (^) Specify Object Counts: Pressing the Count button provides current row counts. You
can manually enter numbers if the current data source is different from the target
design (for example, a small development data set).
■ Set Aggregation Options: Options on the left tell the designer when to stop creat-
ing new aggregations. Press the Continue button to create an aggregation design
before pressing the Next button.
No strict rules exist, but some general guidelines may help:
■ Target an initial performance gain of 10–20 percent. On the most complex cubes,
this is diffi cult to obtain with a reasonable number of aggregations. Keep the
total number of aggregations under 200.
■ (^) Look for a fl attening of the curve in the storage/performance graph and
stop there.
■ (^) Completing the Wizard: Give the new aggregation design a name and optionally
process it.
Best Practice
The best aggregations are usage-based: Collect usage history in the query log and use it to periodi-
cally optimize each partition’s aggregation design. Query logging must be enabled in Analysis Server’s
Server properties, in the Log\QueryLog section.
Aggregations Tab
The toolbar of this tab can launch the wizard and the Usage-Based Optimization Wizard.
The pane toggles between standard and advanced views. Standard view lists all the mea-
sure groups and summarizes which aggregation designs are assigned to which partitions.
The advanced view, as shown in Figure 53-11, enables manual modifi cation of an aggrega-
tion design. Manual updates to a design are generally not effective because usage-based
optimization tends to be more accurate than individual judgment, but cases do arise in
which problem queries can be addressed by a well-placed aggregation. Use the toolbar to
copy an existing design to a new name, and then modify as needed.
Perspectives
A perspective is a view of a cube that hides items and functionality not relevant to a spe-
cifi c purpose. Perspectives appear as additional cubes to the end user, so each group within
the company can have its own “cube,” each just a targeted view of the same data.
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