FILE DECOMPOSITION, REPLICATION AND ASSIGNMENT PROBLEMS HAVE BEEN TREE OF THE PRINCIPAL RESEARCH TOPICS IN PARALLEL AN D DISTRIBUTED PROCESSING. IN THIS PAPER, WE PRESENT THESE PROBLEMS AND PROPOSE A HEURISTIC ALGORITHM FOR DETERMINING EFFECTIVE FILE DECOMPOSITION, REPLICATION AND ASSIGNMENT SOLUTIONS. AT FIRST, A MODEL IS DEVELOPED FOR DECOMPOSING, REPLICATING AND ALLOCATING FILES ON THE DISTRIBUTED SYSTEMS. THE MODEL CONSIDERS STORAGE COSTS, COMMUNICATION COSTS, THE QUERY RATE, UPDATING OF FILES , THE MAXIMUN EXPECTED ACCESS TIME TO FILES AT EACH COMPUTER AND THE WORKLOAD IMBALANCE COST. BECAUSE THESE PROBLEMS ARE IN GENERAL NP-HARD, WE PROPOSE A HEURISTIC ALGORITHM BASED ON GENETIC ALGORITHM TO SOLVE THEM. SEVERAL EXAMPLES FOR DIFFERENT DI