Performance gains using subpages for cache coherency control

When implementing a shared disk database management system, one of the major problems is how to realize an efficient cache coherency mechanism. Most of the solutions proposed use pages as the granularity for concurrency and coherency control. Under high data contention this granularity is not capable of achieving the scalability goal. We describe a new approach called Virtual DataBase Cache, that maintains concurrency control and cache coherency at subpage level in order to reduce data contention. VDBC allows multiple readers and multiple writers concurrently on a page. It also supports different subpage sizes for different tables resp. segments. Our extensive performance analysis, which is presented, clearly shows that our approach is superior to a page based method.