分布式实时事务提交协议

在分布式实时数据库系统中，保证事务原子性的唯一途径是研究和开发出一个实时的原子提交协议．首先详细分析了事务因数据访问冲突而形成的各种依赖关系，在此基础上提出了实时的原子乐观提交协议——2SC协议，该协议减少了事务的等待时间，提高了事务的并发度，且能无缝地和现有的并发控制协议集成在一起，保证事务的可串行化和原子性．通过模拟实验研究表明，采用该协议能够减少超过截止期的事务数目。

A DISTRIBUTED REAL-TIME TRANSACTION COMMIT PROTOCOL

In a distributed real time database system, the only way to ensure transaction atomicity is to investigate and develop a real time atomic commit protocol. An optimistic real time commit protocol, i.e. , Double Space Commit (2SC) is proposed, which is specifically designed for the high performance distributed real time transaction. 2SC allows transactions to optimistically access the data held by the committing transaction in a controlled manner. The controlled access reduces the data inaccessibility and the priority inversion that is inherent in distributed real time commit processing. When the prepared transaction aborts, only the transactions in its abort dependency set abort while the transactions in its commit dependency set will execute as normal. Extensive simulation experiments have been performed to compare the performance of the 2SC with other protocols such as the base protocol, the permits reading of modified prepared data for timeliness (PROMPT), and the deadline driven conflict resolution (DDCR). The simulation results show that 2SC has the best performance. Furthermore, it can seamlessly integrate with concurrency control protocol in existence, which can ensure transaction serialization and atomic commitment.