Using Subpages for Cache Coherency Control in Parallel Database Systems

. Increasing requirements such as higher transaction rates, shorter response times etc., make it necessary to parallelize existing database management systems and to implement them on multiprocessors. Shared memory multiprocessors are not arbitrarily scalable, and thus do not meet future requirements. Therefore, it makes sense to implement databases on large-scale distributed memory multicomputers. This raises the problem how to implement a database cache which uses shared memory concepts extensively under such a hardware architecture. In this paper we describe a solution for this problem by introducing a virtual database cache (VDBC). The VDBC is an algorithmic approach based on the lazy release consistency model used in virtual shared memory systems and on the transaction concept. Additionally, the VDBC uses pages subdivided into equal sized subpages to maintain concurrency control and cache coherency and to reduce data contention on often accessed pages. The advantage of using subpa..