Research On Recovery Strategy Of Embedded Mobile Real-time Database System

With the rapid development of embedded technique and mobile technique, the performance of embedded mobile devices has been greatly enhanced. Various applications have more and more requirements on real-timing. Embedded Mobile Real-time Database System which integrates the mobile computation, real-time application and traditional database technology become a focus in the research of database, in which recovery technique is the key technique. The recovery system in this system should consider about the limitation of resource, time and efficiency, so that the recovery could fit the demand of real-time and mobile characteristic.Besides maintaining the characteristics of traditional recovery, the mobile real-time recovery should focus on how to store the log file in mobile hosts and base stations, strategy of handoff, and strategy of checkpointing. Algorithms for Recovery based on 2-Level Log Using Ephemeral Log & Dynamic Checkpoint Frequency (AR-2LL-ELDCF) is an effectual strategy of recovery in embedded mobile real-time database.AR-2LL-ELDCF uses ephemeral log and only store in-use ephemeral log, which is useful at ordinary recovery, in mobile hosts. The overdue ephemeral log is transferred to base stations to store for the needs of audit. If the in-use ephemeral log is too large to store in the mobile host, it is sent to the base station. In this case it is needed to download the in-use ephemeral log to mobile host before recovery.AR-2LL-ELDCF uses dynamic checkpointing frequency to control the size of in-use ephemeral log, so that it can be completely stored in the mobile host as far as possible. The strategy of handoff is closely cooperating with the stategy of in-use ephemeral log transfer, which can reduce the recovery time.