Research on recovery strategy in embedded real-time main memory databases

Abstract

In order to recover data from embedded real-time main memory databases effectively and efficiently, this paper proposes a real-time log-based recovery approach. With respect to the real-time requirement in embedded systems, we classify the consistency in real-time main memory databases into data and transaction consistencies, analyze them theoretically, design rules for correct recovery strategy, and propose real-time log-based recover algorithms for different types of transactions. The experiments show that the proposed approach is more effective and efficient than methods in both traditional and eXtremeDB database systems.Keywords: Embedded system, Real-time main memory database, Recovery strategy, Consistency ReviewWith the development of embedded systems, the application of databases in embedded systems [1] is a hotspot in both industry and academia. Embedded systems work in an environment without manual intervention, so when a fault occurs in these systems, they need to diagnose the fault and recover it automatically all by themselves [2]. The main memory databases [3,4] can reduce the I/O operations greatly while running, and satisfy the real-time requirement of embedded systems, so the databases implemented in embedded systems usually work in the main memory.In real-time main memory databases [5][6][7], the main copy of database works in the volatile RAM, and the data is very vulnerable, so the recovery is necessary. Meantime, the I/O operations in real-time main memory databases are few, and recovery is the only part that affects the I/O performance, so the performance of recovery is critical for real-time main memory databases [8,9]. While recovering from a fault, real-time main memory databases need to satisfy multiple constraints [10,11], and this pose a huge challenge for designing reasonable recovering strategies.Checkpoint or memory snapshots [12, 13] is a commonly used program recovery strategy, but the overhead of storing states of running program is very high, and it is not suitable for embedded applications. In addition, the logs in embedded systems record the behaviors of embedded systems, and researchers use different logs to design different recovery strategies, such as partition log [14], real-time log [15], remote log [16], and operation log [17]. However, these strategies only take the requirement of real-time into consideration, and ignore other specific requirements in embedded systems, so they cannot be applied to the embedded environment efficiently. In addition, the method proposed in [13], studied the recovery strategy in main-memory, but the method is based on virtual memory snapshots. In order to improve real-time ability, Levy and Silberschatz [18] proposed an incremental recovery strategy in mainmemory database.In this paper, we analyze the consistency constraints in embedded real-time main memory databases from the perspectives of both data and transaction. Then we design some rules that an efficient recovery strategy must obey in embedded real-time main memory database...