移动实时数据库系统中的更新分发

数据广播作为移动计算环境下有效的数据分发技术已有许多研究，当数据广播用于发送不断更新的数据时称它为更新分发．现有的更新分发协议因没有考虑实时数据库系统中数据和事务的定时要求而不适合移动实时只读事务的处理．重点研究了移动实时数据库系统中更新分发的问题，提出了混合前向多版本数据广播协议，该协议在保证事务一致性的同时满足了数据和事务的定时约束．模拟实验表明，该协议能够有效地降低事务错过率和提高数据流行性，较现有更新分发协议更适合移动实时只读事务的处理．

Updates Dissemination in Mobile Real-Time Database Systems

Data broadcast is a widely accepted data dissemination method for mobile computing systems and has held a lot of interest of relevant researchers. When data broadcast is used to disseminate frequently-updated data it is called updates dissemination. Existing updates dissemination protocols are unsuitable for mobile real-time read-only transaction processing because they don't consider the real-time constraints on both data and transactions in mobile real-time database systems. In this paper a new updates dissemination protocol called hybrid forward multi-version data broadcast(HFMVB) is proposed. HFMVB not only guarantees the consistency of read-only transactions,it also provides higher data currency and lower miss rate by shortening the consistency interval, instantly broadcasting updates and utilizing broadcast on-demand. Simulation results show that HFMVB has better performance compared with the existing updates dissemination protocols and is more appropriate for mobile real-time database systems.