As part of the Starburst extensible database project developed at the IBM Almaden Research Center, we designed and implemented a memory-resident storage component that co-exists with Starburst's diskoriented storage component. The two storage components share the same common services, such as query optimization, transaction management, etc. However, the memory-resident storage component is faster than the disk-oriented storage component and hence needs faster run-time services. This paper examines two runtime services, the lock manager and the latch mechanism, and investigates possible cost-cutting measures. We propose the use of of a single latch for protecting a table, all of its indexes, and all of its related lock information, in order to reduce storage component latch costs. We then show that although a table-level latch is a large granule latch, it does not significantly restrict concurrency. We also examine traditional lock manager design and suggest a different design that is a...

While the B-tree (or the B+-tree) is the most popular index structure in disk-based relational database systems, the Ttree has been widely accepted as a promising index structure for main memory databases where the entire database (or most of them) resides in the main memory. However, most work on the T-tree reported in the literature did not take concurrency control into consideration. In this paper, we report our study on the performance of the main memory database index structure that allows concurrent accesses of multiple users. Two concurrency control approaches over the T-tree are presented. The results of a simulation study indicate that the B-link tree, a variant of the widely used B-tree index will outperform the T-tree if concurrency control is enforced. This is due to the fact that concurrency control over a T-tree requires more lock operations than that of a B-link tree, and the overhead of locking and unlocking is high.