Update Cubes Incrementally

It is best to place frequently updated data in one or more separate data sources, so that you can perform incremental updates to quickly add the latest changes to your existing cube.

Tip: Make sure that your data sources contain only new data; otherwise, data duplicated in your source files will be duplicated in the cube.

Incremental updates can save processing time. However, you must consider the following:

  • The first time you run an incremental update, include all the categories for the levels used for partitioning. This ensures the best performance from an incrementally updated cube.
  • If you add new categories to a partition level in a model, the new categories are stored in the parent partition level.
  • If you add a large number of new categories, the access time for report users may be adversely affected because of the increased size of the summary cube. Also, over time, if new categories are introduced, the incremental updates may reduce the effectiveness of the partitioning scheme in the cube, which degrades performance. In either of these cases, we recommend that you repartition your model.
  • After the first incremental update, Cognos® Transformer reverts to using the less-effective Categories method, rather than the Auto-partitioning method.
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

  • do not delete a leaf category, or use Exclude, Cloak, Summarize, or Apex in a view, if this would cause leaf categories to be removed from the cube
  • 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.