Traffic data while the system is in operation is collected for a certain time as a preprocess. Typical patterns are extracted from the collected traffic data. Next, stream programs are created for the individual typical patterns and stored for the future reference. Next, the IDs of alternative tasks for transition among different stream programs are stored. In actual system operation, the system measures traffic data regularly or at any time, compares the resultant patterns with the typical patterns, and selects a stream program corresponding to the closest typical pattern as the next phase. Program shutdown time when shifting from the stream program in the present phase to the next phase can be reduced by gradually shifting empty tasks in the present phase to the next stream program as alternative tasks in consideration of the cost of switching between tasks, the cost of transferring data among resources, and so on.