Abstract:

According to the real time characteristics and criticality of transaction, it is classified as hard real-time transaction, firm real-time transaction,  soft real time transaction and non-real-time transaction. The traditional concurrency control strategy only considers one or two kinds of transactions,  and considers the firm/soft real-time transaction as a unique soft real-time transaction, which features non-preclsion badly and then decreases system   throughout. So, this paper brings forward an adaptive concurrency control mode for mixed transactions. The mode adopts a two-level concurrency control a rchitecture, one level is a primary concurrency controller which detects probably existing data conflicts among different kinds of transactions; another is a subordinate concurrency controller which explores probably existing data conflicts amongst the same kind of transactions and serves as four subord  inate concurrency controllers. Every controller uses a different control strategy due to the different properties of every transaction, so the system th   roughout ultimately, but it needs extra hardware as to be provided with maximum adaptability and to enhance overhead.

Key words: parallel and real-time database system, adaptive concurrency control, optimistic concurrency control, subtransaction scheduling