Improving Predictability of Transaction Execution Times in Real-time Databases |
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Authors: | Rastogi Rajeev Seshadri S Bohannon Philip Leinbaugh Dennis Silberschatz Avi Sudarshan S |
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Affiliation: | (1) Bell Laboratories, 600 Mountain Avenue, Murray Hill, NJ, 07974-0636;(2) Computer Science and Engineering Dept., Indian Institute of Technology, Bombay, India |
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Abstract: | We present a design for multi-versionconcurrency control and recovery in a main memory database, anddescribe logical and physical versioning schemes that allowread-only transactions to execute without obtaining data itemlocks or system latches. Our schemes enable a system to providethe guarantee that updaters will never interfere with read-onlytransactions, and read-only transactions will not be delayeddue to data contention. Consequently, transaction executionsbecome more predictable—this partially alleviates a majorproblem in real-time database system (RTDBS) scheduling, namely,significant unpredictability in transaction execution times.As a result, in addition to a transaction's deadline, a moreaccurate estimate of its execution time can also be taken intoaccount, thus facilitating better scheduling decisions. Our contributionsinclude several space saving techniques for the main-memory implementation,including improved methods for logical aging of data items andthe introduction of physical aging for low-level structures.Some of these schemes have been implemented on a widely-usedsoftware platform within Lucent, and the full scheme is implementedin the Dalí main-memory storage manager. |
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Keywords: | transactions versioning concurrency-control aging consistency locking timestamps deadlines |
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