Resolving executing-committing conflicts in distributed real-time databasesystems

In a distributed real-time database system (DRTDBS), a commit protocol is r equired to ensure transaction failure atomicity, If data conflicts occur be tween executing and committing transactions, the performance of the system may be greatly affected, In this paper, we propose a new protocol, called d eadline-driven conflict resolution (DDCR), which integrates concurrency con trol and transaction commitment management for resolving executing and comm itting data conflicts amongst firm real-time transactions, With the DDCR, a higher degree of concurrency can be achieved, as many data conflicts of su ch kind can be alleviated, and executing transactions can access data items which are being held by committing transactions in conflicting modes, Also , the impact of temporary failures which occurred during the commitment of a transaction on other transactions, and the dependencies created due to sh aring of data items is much reduced by reversing the dependencies between t he transactions, A simulation model has been developed and extensive simula tion experiments have been performed to compare the performance of the DDCR with other protocols such as the Opt [1], the Healthy-Opt [2], and the bas e protocol, which use priority inheritance and blocking to resolve the data conflicts, The simulation results show that the DDCR can significantly imp rove the system performance under different workload and workload distribut ions. Its performance is consistently better than the base protocol and the Opt protocols in both main-memory resident and disk-resident DRTDBS.