A cost-based buffer replacement algorithm for object-oriented database systems

Many object-oriented database systems manage object buffers to provide fast access to objects. Traditional buffer replacement algorithms based on fixed-length pages simply assume that the cost incurred by operating a buffer is proportional to the number of buffer faults. However, this assumption no longer holds in an object buffer where objects are of variable-lengths and the cost of replacing an object varies for each object. In this paper, we propose a cost-based replacement algorithm for object buffers. The proposed algorithm replaces the objects that have minimum costs per unit time and unit space. The cost model extends the previous page-based one to include the replacement costs and the sizes of objects. The performance tests show that the proposed algorithm is almost always superior to the LRU-2 algorithm and, when significant replacement cost is involved, is more than twice as fast. (C) 2001 Published by Elsevier Science Inc.