Analysis of overflow handling for variable length records

摘要

Although files with variable length records are very frequent in actual databases due to variable length fields, missing attribute values, multiple values of an attribute and compression, little has been reported in the literature about file structures appropriate for variable length records. In this paper we describe and analyze several overflow handling techniques for the case when records are of variable length. We develop analytic models that take into account variable length records and study the performance in the context of indexed sequential (ISAM) files. We also propose a new overflow handling technique and show that it provides an incremental reorganization capability appropriate for handling variable length records. Analytic results demonstrate that its performance is better than the performance of previous methods. The overflow handling techniques and the analytic methods developed in this paper are also applicable to other file structures with variable length records that require overflow handling.