Abstract: The concurrency control algorithm can guarantee the isolation and consistency of transactions when multiple users access the same date at database simultaneously.This paper proposed an adaptive decision concurrency control algorithm to solve the problem of poor adaptability in existing concurrency control algorithms.This algorithm divides its concurrency control process into two phases:the execution authorizing phase and the strategy selecting phase.In the exe-cution authorizing phase,the algorithm compares effectiveness of transactions to determine the execution order of conflicting transactions.After that,the algorithm selects optimistic/pessimistic conflict resolution strategy dynamically according to the transactions’ read/write status and the current conflict rate in the strategy selecting phase.DDCC algorithm has high efficiency no matter whether the system is busy or idle.Performance tests show that DDCC algorithm proposed in this paper is superior to classical strict two phases locking algorithm and hybrid concurrency control algorithm.

Key words: Concurrency control,Dynamic decision,Conflict-rate prediction,Conflict resolution