Incremental Recovery in Main Memory Database Systems

In traditional database management systems, recovery activities, like checkpointing and restart, are performed in a quiescent state where no transactions are active. This approach impairs the performance of on-line transaction processing systems. Recovery related overhead is particularly troublesome in an environment where a large volatile memory is used. The appealing alternative is to perform recovery activities incrementally and in parallel with transaction execution. An incremental scheme for recovery in main memory database systems is presented in this paper. We propose a page-based incremental restart algorithm that enables the resumption of transaction processing as soon as the system is up. Pages are recovered individually and according to the demands of the post-crash transactions. In addition, an incremental method for propagating updates from main memory to the backup database on disk is also provided. Here the emphasis is on decoupling the I/O activities related to the propagation to disk from the forward transaction execution in memory. Finally, we construct a high-level recovery manager based on operation logging on top of the low-level page-based algorithms. The algorithms we propose are motivated by the characteristics of main memory database systems, and exploit the technology of non-volatile RAM.