关键词: 实时数据库, 并发控制, 可推测并发控制, 优先级升级

Abstract: Successful submission before deadline is the key ingredient for applications in Real-Time DataBase Management Systems（RTDBMS），while traditional DBMS focuses main on the opposite goal of high throughput of the system.A two-Phrase Speculative Concurrency Control approach based on the deadline（PSCC） is therefore addressed to raise the successful submission for real-time transactions under stringent time constraints.By achieving a tradeoff between the optimistic concurrency control and the passive concurrency control，the PSCC can speculate on the suspicious conflicts according to their deadline，restart transactions with more possibility to imperil the DB consistency while allowing those to execute continually with less possibility.At the verification phrase of the transaction，the broadcasting approach is used to guarantee the DB consistency as the OCC-BC does，but those transactions violating submission consistency rule will be temporarily blocked and a priority escalation approach is used to avoid the restarting of blocked transactions.Finally，the algorithms of PSCC are designed.Performance evaluations show that by using PSCC algorithms，the missing rate and restarting probability can be reduced than using OCC-BC and HPA.

Key words: real-time database systems, concurrency control, speculative concurrency control, priority escalation