At this stage a detailed analysis is performed on the result of pass 0. The purpose of this step is to refine the calibration constants. Periodically it will be necessary to re-analyze a subset of the events with new calibration constants to assess their impact on data quality. This reassesment would be identical to step 1, in which several hundred thousand events are analyzed from a variety of data files from throughout the running period. The off-line database and monitoring histograms can then be inspected to gauge the impact of the new, refined calibration constants. Another activity that takes place during this process is the development of a new production library to be used for final data analysis. Quite often, code refinements need to be made or new calibration procedures are added and these additions need to be incorporated into the software build. When the running group is satisfied with the quality of the calibrations, presumably after several iterations, one can proceed to the final step.