IBM Cognos, User Manual, Page: 197 / 411

Procedure
1.
Let Cognos Transformer auto-partition your cube, leaving the optimization
settings at their defaults.
2. In the resulting log file, note the partition points selected by the
auto-partitioning algorithm.
Generally, the dimensions with the most levels offer the greatest possibility for
consolidation. Review the difference between the row and category counts in
the
Start Count and Consolidation and End Count and Consolidation lines,
comparing records consolidated between
Pass 0
and the last pass (usually
Pass 4
or
Pass 5
).
3.
Remove partitioning from your model so you can start testing your manual
alternatives, by clicking
Reset Partitions
on the
Tools
menu.
4. Calculate the required number of partitions, based on the following formula:
Number_of_partitions = Number_of_source_rows / Desired_partition_size
Note: In most production environments, partition levels should not exceed
3
and partition sizes should not exceed
500,000
records. Source rows are based
on the source file.
5. Select a dimension suitable for partitioning. Avoid large flat dimensions,
dimensions with alternate drill-down paths or leaf-level reporting and
dimensions whose categories change frequently, such as the time dimension.
Open the diagram for the selected dimension.
6. Choose a level that contains the approximate number of categories identified
in your calculation, and open the property sheet for each category in that
partition root level.
7.
In each Partition box, type the partition number you want to assign and click
OK .
Note: Although you can assign the same partition number to categories from
different levels, we recommend that you select categories from the same level,
and manually set no more than three levels of partitioning.
8. Assign the same number to each category in the partition level, starting with
the lowest level and working up to the top level in the dimension.
Make sure that each partition level number is equal to, or one greater than,
the partition number of its ancestor. You are warned of any gaps in the
numerical order of the partitions when you create the cube.
Note: Manually-specified partition level numbers do not necessarily define
the order in which partitions are placed in the cube. Partition level numbers
may be reordered by Cognos Transformer.
9. On the PowerCube property sheet, click the Auto-Partition tab and specify a
Maximum number of passes that is at least as large as the number of
partitions you added in the previous step.
10. Create the cube, analyze the log file to see if the number of records and
categories decreases from pass to pass and, if there is no decrease in the
number of records on the last pass, reduce the
Maximum number of passes
value by one, or increase the desired partition size. If both the summary and
Level 1
partitions have the same number of records, indicating that the
summary partition was not consolidated, try increasing the Maximum
number of passes .
11. Use the PowerCube Partition Status command on the Tools menu to view the
distribution of records. For each applied partition level (beginning with
0
), a
Chapter 8. PowerCubes in Production Environments
183