Heuristic methods for the data placement problem

Databases require a management system which is capable of retrieving and storing information as efficiently as possible. The data placement problem is concerned with obtaining an optimal assignment of data tuples onto secondary storage devices. Such tuples have complicated interrelationships which make it difficult to find an exact solution to the present problem in a realistic time. The authors therefore consider heuristic methods-three of which are discussed and compared-the ‘greedy’ graph-collapsing method, the probabilistic hill-climbing method of simulated annealing and a third ‘greedy’ heuristic, the random improvement method, which is a local search heuristic. Overall, the best performance is obtained from the graph-collapsing method for the less complicated situations, but for larger-scale problems with complex interrelationships between tuples the simulated annealing and random improvement algorithms give better results.