Database Reference
In-Depth Information
Table 12-2.
The Review Aggregation Usage Options
Option
Description
Estimated storage reaches
Limits the aggregations based on the maximum hard drive space devoted to
them, in either megabytes (MB) or gigabytes (GB).
Performance gain reaches
Limits the aggregations based on the estimated performance gain percentage.
Clicking Stop
Limits the aggregations by clicking Stop during the selection process.
(This option was more useful a decade ago when the selection process took
longer to run.)
Do not design aggregations (0%)
Specifies that there are no aggregations. This option allows you to clear an
existing aggregation.
The buttons at the bottom of this dialog window were not necessarily obvious when you first encountered
this dialog window, but they make sense in the context of how the aggregation selection process works. The Start
button, of course, begins the aggregation selection process, and the Stop button ends this process. However, note
that the Start button changes to the Continue button while the selection process is active.
After the selection process has run its course, some aggregations will have been chosen. Clicking
Next moves you to the Completing the Wizard dialog window. If you would like to make a change, such as
increasing the space available for aggregations and running the selection process one more time, the Reset
button allows you to clear all the aggregation choices and begins running Microsoft's selection algorithm
once more.
In the last wizard dialog window, you can specify the name of this particular aggregation design. In
Figure
12-23
we have chosen to call it
SimpleAggregationDesign
to indicate that it is a preliminary choice
that we may revisit at a later point in time. In the lifecycle of the cube's partitions, you may need to adjust the
aggregation rules to fine-tune the report versus processing performance. Remember that increasing stored
aggregations may increase report performance, but it will be at the cost of the time it takes to process the
partition, because the aggregations are created and stored during the processing.
■
It may take several attempts to get the balance right in a production environment. Remember that
your reports will always be able to pull aggregations from the ssAs server. no matter what you do, your reports will
still look the same. What is being configured is how many aggregations will be stored on the hard drive, not how
many aggregations will be available for your reports.
Important
