替代和补偿是实时事务的两个基本特点，也是并发控制的主体，同时给并发控制带来了新的问题。AC—BasedOCC—FV协议把替代和补偿综合到乐观并发控制协议OCC-FV中来，对于处于接纳队列中的每个事务，尽可能地选择无冲突替代进入就绪队列，但这只是一个理想情况。如果冲突不可避免，不仅要选择一个合适替代参与并发控制，即使冲突发生时，也要确保系统始终处于一个安全状态。在冲突消解时，结合补偿的特点，对乐观并发控制协议OCC-FV进行了扩展，当事务失败后，立即调度相应补偿事务，以防止系统灾难的发生。%Alternative and compensation are two basic Characteristics of the real-time transaction, also are body of the concurrence control. At the same time, new problems are brought. AC-Based OCC-FV associates alternative and compensation with optimistic concurrency control OCC-FV. For each transaction in accepted queue, An alternative which cause no conflict can be chosen to join the ready queue as soon as possible. This is just a kind of ideal circumstance. If the conflict can not be avoided, a suitable alternative not only be chosen to join the concurrent control, although conflicts take place, the system always can also be kept in a safe state. And the optimistic concurrent control OCC-FV extending with compensation is adopted to resolve the conflicts, keeping system from catastrophe.
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