Ryoji Kataoka

A multiversion concurrency control algorithm for concurrent execution of partial update and bulk retrieval transactions

A novel multiversion concurrency control algorithm is presented which substantially improves concurrency between batch and online transactions. A bulk retrieval transaction which reads all data objects and partial update transactions which read and write a few data objects are studied as batch and online transactions, respectively. The algorithm is based on a mixture of multiversion time-stamp ordering and modified two-version two-phase locking. It can remove the interference between the retrieval and the update transactions, and reduce the interference between the update transactions themselves. Results of a simulation study show that the completion ratio of those transactions with this algorithm is much better than that with existing algorithms, when the number of transactions is large and the data contention between those transactions is high.<<ETX>>

Priority management for concurrent execution of real‐time and on‐line transactions

This paper presents priority management methods for concurrent execution of real-time transactions with timing constraints and on-line transactions without timing constraints in a real-time database system (RTDBS). The aim of this study is the meeting of deadlines of real-time transactions and shortening the response time of on-line transactions at the same time. The proposed methods are Simple Mix, Biased Mix, and Balanced Mix, each of which differs in its strategy for assigning priorities to on-line transactions. Simulation results show that Balanced Mix, which determines priorities dynamically according to the slack of real-time transactions, can shorten the response time of on-line transactions while keeping the deadline-missing ratio of real-time transactions low.

A new multiversion concurrency control algorithm for partial update transactions and bulk retrieval transactions

With the advanced use of databases, on-line and batch transactions are executed concurrently. Then a demand arose for the concurrency control method which can realize the excellent on-line transaction processing independently of the batch transactions. The multiversion concurrency control is suitable for such a requirement. This paper proposes a new multiversion concurrency control algorithm which has a high concurrency between the partial update transactions, which is a typical on-line transaction, and the bulk retrieval transactions, which is a typical batch transaction. The algorithm is based on a mixture of an improved two-version, two-phase locking and the multiversion time stamp ordering. It is shown as simulation results that the proposed algorithm is better than the traditional ones in terms of the completion ratio of the partial update and the completion ratio of the bulk retrieval, independently of the number of partial updates executed concurrently. It is shown also that the algorithm is better than the traditional ones in such an environment since the data contention between partial update transactions is high.