Choice of the optimal number of blocks for data access by an index

摘要

A computational algorithm with the aim of reducing access costs in database and file system applications is presented. The idea being developed is to determine the optimal number of contiguous data blocks, that is the multiblocking factor, to be transferred to memory in a single access. This choice is not effected for each file or relation, but a multiblocking factor will be selected independently for each index of a relation or of a file. The determination of different values is effected in order to increase the percentage of useful information transferred during each access and, therefore, to decrease the total number of I/O operations. The effectiveness of the method is shown by the experimental results obtained using an actual database. The selection criterion of the multiblocking factor associated with an index is based on the measurement of the average clustering of the key value occurrences in the stored records.