INCREMENTAL RECOVERY IN MAIN MEMORY DATABASE-SYSTEMS

Recovery activities, like checkpointing and restart, in traditional database management systems are performed in a quiescent state where no transactions are active. This approach impairs the performance of on-line transaction processing systems. This 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 (MMDB's) 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. A method for propagating updates from main memory to the backup database on disk is also provided. The emphasis is on decoupling the I/O activities related to the propagation to disk from the forward transaction execution in memory. We also construct a high-level recovery manager based on operation logging on top of our page-based algorithms. The algorithms we propose are motivated by the characteristics of large MMDB's, and exploit the technology of nonvolatile RAM.