Difference between BW statistcs for a cube and for overall system

Hai all,

We have a BW system with a process chain for Bw statistics for the whole system. I made a process chain with DB statistics for one my cube. I am sorry. I have little knowledge of the statistics.

My question is would be useful to have statistics for the whole system or perhaps a BW statistics cube

or

Constructing DB statistics every time when cube is loaded?

Which one is advantageous and more recommended? I would appreciate if somebody could refer me to some kind of documentation on this topic.

Thank you very much.