提出了适用于无共享结构并行数据库实时多版本两阶段封锁并发控制协议.该协议具有多版本并发控制机制与两阶段封锁机制的优点,使用如下策略以减少延误截止时间事务数量:若冲突集中有比持锁事务Ti优先级高的事务,且Ti重启动不会延误截止...提出了适用于无共享结构并行数据库实时多版本两阶段封锁并发控制协议.该协议具有多版本并发控制机制与两阶段封锁机制的优点,使用如下策略以减少延误截止时间事务数量:若冲突集中有比持锁事务Ti优先级高的事务,且Ti重启动不会延误截止时间,则Ti重启动,冲突集中优先级最高的事务获得锁;否则,冲突集中其他事务等待.通过仿真模拟,与HP2PL和OCC TI WAIT 50协议进行比较,结果表明:在正常负载、长短事务混合的情况下,并发控制协议能有效地降低事务延误截止时间率、事务重启动率,减少同步开销,该协议比HP2PL和OCC TI WAIT 50协议性能更好,同时具有较强的扩展性.展开更多
在并行实时数据库中,并发控制协议不仅要满足数据库一致性约束,而且要满足时间约束。本文提出了实时多版本两阶段封锁并发控制协议,它能有效地减少延误截止时间事务数量。作者通过仿真模拟,在共享磁盘体系结构下与HP2PL和OCC TI WAIT 5...在并行实时数据库中,并发控制协议不仅要满足数据库一致性约束,而且要满足时间约束。本文提出了实时多版本两阶段封锁并发控制协议,它能有效地减少延误截止时间事务数量。作者通过仿真模拟,在共享磁盘体系结构下与HP2PL和OCC TI WAIT 50协议进行了比较。实验结果表明,该协议比HP2PL和OCC TI WAIT 50协议性能更好。展开更多
A DMVOCC-MVDA （distributed multiversion optimistic concurrency control with multiversion dynamic adjustment） protocol was presented to process mobile distributed real-time transaction in mobile broadcast environment...A DMVOCC-MVDA （distributed multiversion optimistic concurrency control with multiversion dynamic adjustment） protocol was presented to process mobile distributed real-time transaction in mobile broadcast environments. At the mobile hosts, all transactions perform local pre-validation. The local pre-validation process is carried out against the committed transactions at the server in the last broadcast cycle. Transactions that survive in local pre-validation must be submitted to the server for local final validation. The new protocol eliminates conflicts between mobile read-only and mobile update transactions, and resolves data conflicts flexibly by using multiversion dynamic adjustment of serialization order to avoid unnecessary restarts of transactions. Mobile read-only transactions can be committed with no-blocking, and respond time of mobile read-only transactions is greatly shortened. The tolerance of mobile transactions of disconnections from the broadcast channel is increased. In global validation mobile distributed transactions have to do check to ensure distributed serializability in all participants. The simulation results show that the new concurrency control protocol proposed offers better performance than other protocols in terms of miss rate, restart rate, commit rate. Under high work load （think time is ls） the miss rate of DMVOCC-MVDA is only 14.6%, is significantly lower than that of other protocols. The restart rate of DMVOCC-MVDA is only 32.3%, showing that DMVOCC-MVDA can effectively reduce the restart rate of mobile transactions. And the commit rate of DMVOCC-MVDA is up to 61.2%, which is obviously higher than that of other protocols.展开更多
文摘提出了适用于无共享结构并行数据库实时多版本两阶段封锁并发控制协议.该协议具有多版本并发控制机制与两阶段封锁机制的优点,使用如下策略以减少延误截止时间事务数量:若冲突集中有比持锁事务Ti优先级高的事务,且Ti重启动不会延误截止时间,则Ti重启动,冲突集中优先级最高的事务获得锁;否则,冲突集中其他事务等待.通过仿真模拟,与HP2PL和OCC TI WAIT 50协议进行比较,结果表明:在正常负载、长短事务混合的情况下,并发控制协议能有效地降低事务延误截止时间率、事务重启动率,减少同步开销,该协议比HP2PL和OCC TI WAIT 50协议性能更好,同时具有较强的扩展性.
文摘在并行实时数据库中,并发控制协议不仅要满足数据库一致性约束,而且要满足时间约束。本文提出了实时多版本两阶段封锁并发控制协议,它能有效地减少延误截止时间事务数量。作者通过仿真模拟,在共享磁盘体系结构下与HP2PL和OCC TI WAIT 50协议进行了比较。实验结果表明,该协议比HP2PL和OCC TI WAIT 50协议性能更好。
基金Project(20030533011)supported by the National Research Foundation for the Doctoral Program of Higher Education of China
文摘A DMVOCC-MVDA （distributed multiversion optimistic concurrency control with multiversion dynamic adjustment） protocol was presented to process mobile distributed real-time transaction in mobile broadcast environments. At the mobile hosts, all transactions perform local pre-validation. The local pre-validation process is carried out against the committed transactions at the server in the last broadcast cycle. Transactions that survive in local pre-validation must be submitted to the server for local final validation. The new protocol eliminates conflicts between mobile read-only and mobile update transactions, and resolves data conflicts flexibly by using multiversion dynamic adjustment of serialization order to avoid unnecessary restarts of transactions. Mobile read-only transactions can be committed with no-blocking, and respond time of mobile read-only transactions is greatly shortened. The tolerance of mobile transactions of disconnections from the broadcast channel is increased. In global validation mobile distributed transactions have to do check to ensure distributed serializability in all participants. The simulation results show that the new concurrency control protocol proposed offers better performance than other protocols in terms of miss rate, restart rate, commit rate. Under high work load （think time is ls） the miss rate of DMVOCC-MVDA is only 14.6%, is significantly lower than that of other protocols. The restart rate of DMVOCC-MVDA is only 32.3%, showing that DMVOCC-MVDA can effectively reduce the restart rate of mobile transactions. And the commit rate of DMVOCC-MVDA is up to 61.2%, which is obviously higher than that of other protocols.
