Main Memory Database Recovery Issues

这是持续三年的奖项中的第一个。半导体存储器不断增大的体积和不断降低的成本促使人们对驻留在存储器中的数据库进行研究。这些内存数据库(MMDB)系统的目标是高吞吐量应用，例如机票预订系统、电话交换数据库和其他实时系统，其中内存驻留数据的可用性是至关重要的。要使用易失性RAM实现这种高可用性，需要磁盘上的备份归档数据库以及有效的算法，以便在系统故障后将数据库检查点到归档，并将其从归档恢复到主内存。已经证明，使用延迟更新技术的MMDB系统通常执行得更好，其中要更新的数据首先被放置在特殊的非易失性阴影区域中，并且只有在事务提交时才被放置在主存储器中。作者正在使用更传统的即时更新(IU)技术以及延迟更新(DU)策略来研究MMDB数据库的检查点和重载。最好的检查点方法以及部分重载策略将被确定。部分重新加载允许数据库在系统故障后更快地联机，因为在启动系统之前并不是所有的MMDB都重新加载。这项研究是对MMDB系统的部分重新加载技术的第一次检查。由于RAM的易变性，MMDB应用程序的高吞吐量需求，以及部分重新加载可能显著增加数据库系统的正常运行时间，本研究的结果和影响是广泛和重要的。

This is the first of a three year continuing award. The increasing size and decreasing cost of semiconductor memory has prompted research into databases which are memory resident. These Main Memory DataBase (MMDB) systems are aimed at high throughput applications such as airline reservation systems, phone switching databases, and other real time systems where the availability of the memory resident data is crucial. To achieve this high availability with volatile RAM requires a backup archive database on disk as well as efficient algorithms to checkpoint the database to the archive and to recover it from the archive to main memory after a system failure. It has been shown that MMDB systems often perform better with deferred update techniques where data to be updated is first placed in a special nonvolatile shadow area and only at transaction commit time is placed in main memory. The authors are investigating both checkpointing and reloading of MMDB databases with the use of more conventional immediate update (IU) techniques as well as deferred update (DU) strategies. The best checkpointing approaches are to be determined as are partial reloading strategies. A partial reload allows the database to be brought online after a system failure faster because not all of the MMDB is reloaded prior to bringing the system up. This research represents the first examination of techniques for partial reloading of MMDB systems. Due to the volatility of RAM, the high throughput needs of MMDB applications, and the potential for partial reloading to dramatically increase the uptime of database systems, the results and impact of this research are both widespread and significant.