Choosing A Partitioning Strategy - IBM Cognos User Manual

Tip: If your model uses cube groups, and only a subset of them contain data that
has changed since the last update, you can save processing time by disabling the
cube creation option for the unchanged member cubes.
For performance reasons, we recommend that you periodically recreate the entire
cube, to optimize its auto-partitioning scheme (for example, update weekly,
recreate monthly). Also, if you make structural changes to your model, you must
recreate the cube, including its historical summary data, before you can perform
further incremental updates. We therefore recommend that you retain all the data
sources used to create the original cube, so you can point to those sources during
the rebuild.
To avoid invalidating your incrementally updated cubes
v do not delete a leaf category, or use Exclude, Cloak, Summarize, or Apex in a
v do not delete, add, or move a dimension or measure
Procedure
1. Add a new cube definition to the PowerCubes list.
2. Open the property sheet for the new cube and click the Processing tab.
3. Select the This cube is incrementally updated check box and click OK.
4. Create the cube.

Choosing a Partitioning Strategy

Partitioning is an effective way to improve run-time access to cubes and OLAP
reports that have millions of rows of source data. There is a tradeoff, however. The
more partitions there are, the longer it takes to build the cube.
The partitioning process involves multiple passes through the data. Categories are
consolidated and sorted, records in the resulting (temporary) work files are
counted, and the information is divided into rows that summarize the measures at
one or more optimal partition levels.
By default, Cognos Transformer automatically partitions your cubes. However, if
your cubes are very large or unusually structured, or if you have particular
reporting needs, you may want to designate one or more dimensions for manual
partitioning, provided these dimensions have sufficient depth. Flat hierarchies do
not lend themselves to this optimization method, although you can add manual
levels to bring them closer to the ideal parent:child ratio (1 parent to 10 children).
Partitioning is warranted, and will most likely be successful, in the following
circumstances:
v Most of your users' queries can be answered from the first or upper partitions,
v The information required for most queries can be found within a single
v Your dimensions have sufficient depth that the category-per-level ratios are 10:1
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IBM Cognos Transformer Version 10.1.1: User Guide
view, if this would cause leaf categories to be removed from the cube
called summary partitions.
If you partition a dimension for which lowest-level detail reports are needed,
access times will be slower, as the data must be returned from several partitions.
partition.
or less.
If a dimensional hierarchy is too flat, you may have to add manual levels to
bring it closer to the ideal ratio.