Research And Implementation Of Concurrency Controls In MLS/DBMS

With the rapid development of information and technology, database faces more serious security situation. Research in the concurrency controls has been an important part in the field of security database. In this paper, we discuss the theories and the implemention method of concurrency control, present a new multilevel transaction model--- NHSTM and apply this model to the concurrency control mechanism for NHSDB, a multilevel security DBMS prototype.Firstly, in this paper, we review traditional concurrency control mechanism and analysis the advangtages and shortcomings of them. Then, the paper summaries disadvantages of traditional concurrency controls under multilevel security condition and introduces multilevel security dbms concurrency control.After summarizing the related research work, we present a multi level transaction model to solve the convert channel and starvation problems in concurrent control under BLP multi level security model. We analysis the conflict, convert channel and starvation problems of concurrent schedule based on Strict-2PL locking protocal which applies NHSTM model,then present a concurrent scheduling algorithm making use of buffer and point P.Also,we proved the concurrent schedule algorithm is serializable. At the same time,we introduce the key technical used in NHSDB concurrency control mechanism,and give the implementation details. Finally, we draw a conlusion for this paper and future direction in this field.