Recovery Technology For Active Real-time Embedded Main Memory Database ARTs-EDB

ARTs-EDB seamlessly integrates traditional databases, real-time databases as well as activeness rule concepts, techniques and mechanisms. In order to guarantee the executions of real-time transactions, ARTs-EDB is based on Main Memory Database (MMDB) technology. In a MMDB, the primary copy of the database resides in volatile main memory. This makes MMDB systems more vulnerable to failures compared to the traditional Disk Resident Databases (DRDB). The active real-time database management system ARTs-EDB is what this thesis focuses. Based on the architecture of ARTs-EDB, the implementation strategy and design scheme of recovery system is brought forward.A backup copy of the database is maintained in secondary storage for recovery purposes. Recovery activities like logging, checkpointing, backup and reloading are used to restore the database to a consistent state after a system crash has occurred. In ARTs-EDB, REDO logs are maintained in main memory for active transactions. Once a transaction is committed, the logs are saved in stable memory. The logging capacity decreases. A recovery scheme with action consistent checkpointing is combined in ARTs-EDB recovery model, which simplifies the location of the very starting point in the recovery process. It can save recovery cost and restart the whole system as soon as possible. This is of great value in real-time database system, for the fast database recovery can meet the real-time transaction deadline well, and reduce the missing deadline rate of real-time transactions efficiently. The vulnerability of MMDB makes the reloading of MMDB very important, which influences system performance greatly. According to this, a data priority reload technique is illustrated in detail. Different data reload strategies are chosen according to the data priority the system assigns by their characteristics. Using limited time to get fast and efficient data reload performance can be achieved. Then the ARTs-EDB can be brought up in use just after some high priority data are in main memory in a much shorter period of time. The backup scheme is based upon increment fuzzy backup. This scheme reduces the influence to system.