| As the application of distributed computing is used much more widely,distributed database becomes a significant part of information management．It avoids a lot of disadvantages of conventional centralized database,and is applicable to many situations．Distributed database iS a set ofdata which iS the unity logic,but in fact these data iS located ondifferent sites．It iS of high availability,easy expansibility,highconcurrency,high efficiency and etc． In distributed system,data redundancy iS a method to improve thespeed of query and the availability of system．Distributed query shouldshield the lower level details of data redundancy from end users,distributed transaction should ensure data from disaccord． ThiS paper introduces basic conceptions of distributed databasefirstly,discusses distributed transaction and concurrent control,describes the development prototype MySQL'S characters,architectureand executive mechanism,then shows the skeleton model of DPSQL andexposes the strategy and algorithm of distributed query and distributedtransaction,at last analyzes the extra expenses and response delay ofdistributed processes． ThiS paper exposes the implementation mechanism of distributed queryand distributed transaction emphatically．Distributed query uses thestrategy of"read one,write a11"．S0 in such a system if user'Srequests are read--only for the most part and the distribution of dataredundancy iS plausible, efficiency iS very high．Distributedtransaction uses two-。phase commit protocol to ensure the consistency ofglobal data,which has less communication overhead．... |
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