A Concurrency Control Method for Parallel Btree Structures

Abstract

A new concurrency control protocol for parallel Btree structures, MARK-OPT, is proposed. MARK-OPT marks the lowest structure-modification-operation (SMO) occurrence point during optimistic latch coupling operations, to reduce the cost of SMO compared to the conventional protocols such as ARIES/IM and INC-OPT. The marking reduces the frequency of restarts for spreading the range of X latches, which will clearly improves the system throughput. Moreover, the MARK-OPT is deadlock free and satis- fies the physical consistency requirement for Btrees. These indicate that the MARK-OPT is right and suitable as a concurrency control protocol for Btree structures. This paper also proposes three variations of the protocol, INC-MARKOPT, 2P-INT-MARK-OPT and 2P-REP-MARK-OPT, by focusing on tree structure changes from other transactions. We implement the proposed protocols, the INC-OPT, and the ARIES/IM for the Fat-Btree, a form of parallel Btree, and compare the performance of these protocols using a large-scale blade system. The experimental results indicate that the proposed protocols always improve the system throughput, and the 2P-REP-MARK-OPT is the most useful protocol in a high update environment. Moreover, in the experiment, the low frequency of restarts in the proposed protocols indicates that the marking in the proposed protocols is effective.