When setting up a connection to a an OLAP database in the TARGIT Management client, one of the steps in the connection dialog includes an option for 'Use subcubes'.
In this context, Subcubes is an internal technology used by Microsoft OLAP cubes to generally improve querying performance. The original cube is said to be diced into subcubes when the query's applied filters results in a subset of the cubes data.
By default, the Subcubes setting is enabled to achieve best performance, and should rarely be disabled.
When should subcubes be disabled?
Only in rare occasions, where Totals or Subtotals of calculated members may otherwise show wrong results, the cure may be to disable Subcubes.
If you for any reason disable Subcubes, you should very carefully check your Totals and Subtotals - not only for calculated members, but also for other standard measures and dimensions.
Note: Via decorations, you can also enable/disable Subcubes. If Subcubes is disabled via the OLAP connection properties, the 'Visual totals' setting in Decorations may also be relevant.
Decorations article: Decorations
Also, this external article may help to understand Subcubes: Understanding OLAP Cubes - A guide for the perplexed