The PI System manages years of historical data of process variables, using advanced statistical techniques variability patterns can be found and reason-cause relationships established. Patterns can be further used for variability factor analysis, early alert of sub-standard conditions, fault detection, etc. Using PI DataLink, off-line analysis examples will be shown from mining and pulp and paper applications, also an on-line application that uses the model parameters from the off-line analysis. A vision of the future use of PI ACE for on-line applications will be explained.