Main-memory Database System Based On COM

Main-memory Database System(MMDBS) is a kind of advanced databasetechnology. The thought of Main-memory Database is that load all or most of data ondisk into share memory when system startup, all data operations are carried out inmemory instead of disk,which will reduces the I/O operation remarkbly. The data filestored on disk is just a backup of Main-memory database. Because all data access arecarried out in memory , MMDBS runs much faster than ordinary database system. Ifgive scheduler limit to transaction management of MMDBS, system will have trait ofreal-time database (RTDB). The MMDBS are applied to many fields such asindustrial control, national defense and communication. MMDBS is not simple promotion of ordinary database system but a bran-newdatabase system. Because data access in memory, the algorithms design focuses onthe target of promotion of memory-storage efficiency instead of the target of speed upthe data access. Thus, the data structure especially index structure should be designedover again. Furthermore,data resident in memory is damaged easily when databasesystem crash down, so algorithms design of MMDBS should also target on datarecovery . FlashDB is a implementation of MMDBS. FlashDB loads data from disk toshare memory by a technology called "memory mapping-file",where FlashDBconstructs data table ,record ,field. Hash-index and SB-tree index, which can obtainthe balance of memory usage efficiency and data access speed, are introduced toFashDB. In order to save time of data-query, FlashDB uses the technology parallelquery. Furthermore, FlashDB realizes transaction commit/rollback and data recoveryby using two arraies of object handle , one is main array and the other is backup array.FlashDB is tiny and compact .Client program can load it in form of dynamic linkagelibrary(DLL) which can make the data exchange between client program and FashDBmore fast. FlashDB also takes advantage of orient object programming(OOP) and useinherence ,operator override ,MACRO to realize the mapping between class and tablestructure in database. COM(Component Object Model) technology is also applied toFlashDB, Which is a progress of OOP and supports multiple programming-languagesuch as C,VB,Delphi. The first chapter of this paper introduces origin, peculiarity and status quo ofMMDBS. The second Chapter focuses on the difference between MMDBS andordinary database system, advantage and lack of MMDBS and introduces the moduleand class library of FlashDB. The third and fourth chapter talks about the kernel datastructure, index structure and share memory management algorithms design. Thesetwo chapters are very important because the technology discussed is core ofimplementation of MMDBS . The data structure and index structure of MMDBS isdifferent from that of ordinary database system. The fifth chapter discusses theimplementation of cursor and query optimize, implementation of thread class crossplatform is also discussed. The sixth chapter focuses on transaction management, R/Wlock mechanism and data recovery of MMDBS. The seventh chapter discussesapplication of COM technology to FlashDB and the next step work on FlashDB.