Common ERP systems do not solve the support for workshop management. This paper shows why and under what conditions computer support for workshop schedules is necessary. Demands on the quality of operation plans, factors having an influence on the scheduling process and criteria for selection of appropriate operations are discussed. A verification program was developed for testing the proposed hypotheses. This program proved that a repeated random selection and simulation of the production process could be a good tool for a small number of machines and production tasks. There is no need for sophisticated scheduling for a great number of machines and tasks, operational plans are enough for this purpose.