Concurrent storage structure conversion: from B+ tree to linear hash file

Abstract

Shows that the efficient reorganization of a B+ tree file into a linear hash file can be done concurrently with user transaction processing. This conversion is motivated by a change in database processing, in which efficient sequential and direct access were originally needed, but now only efficient direct access is needed. This is quite reasonable for a database system which accommodates new and changing applications. Several existing database systems, e.g. INGRES, IMS and IDMS allow this type of reorganization, but the reorganization is performed offline. The author devises an algorithm which performs the conversion and presents an analytic model of the conversion process. The author uses a typical database simulation model to evaluate the reorganization scheme. The results from the analytic model are within 3% (on the average) of the observed simulation results.<>