Computer Systems : Steps toward fault - tolerant Real - Time systems , M . Malek
نویسنده
چکیده
Speculative Concurrency Control (SCC) is a new concurrency control approach, especially suited for responsive database systems 5]. SCC uses potentially redundant computations to ensure that serializable schedules are discovered and adopted as early as possible, thus increasing the likelihood of the timely commitment of transactions with strict timing constraints. We present SCC-nS, a generic algorithm that characterizes a family of SCC-based algorithms. Under SCC-nS, shadows executing on behalf of a transaction are either optimistic or speculative. Optimistic shadows execute under an assumed serialization order, which requires them to wait for no other connicting transactions. They execute unhindered until they are either aborted or committed. Alternately, speculative shadows execute under an assumed serialization order, which requires them to wait for some connicting transactions to commit. We single out three SCC-nS family members, which diier in the amount of resources they require, and thus the level of speculation they perform. Finally, we present some simulation results that establish the correlation between speculation and timeliness.
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