Within the last months the semiconductor plant of Infineon in Dresden has converted to a pure manufacturer of logic products. With it, premises for production control have changed to short and, first of all, predictable cycle times. Typical for a logic fab, intelligent performance monitoring and prediction methods have to be installed, coping scheduled and unscheduled disturbances. Most important method is transient fab simulation, giving a 3-months performance forecast based on actual line situation and planned changes in toolset and product mix. This continuous forecast has to be enriched with information to scheduled and unscheduled fab disturbances for just in time initiation of countermeasures in case of foreseeable excursions, e.g. changes in dispatching. In particular, breakdowns have to be analyzed from historical data to find typical patterns, for probability of occurrence and, especially, machine group specific behavior. This paper presents the procedure on the basis of thre...