Optimistic-CC-Performance - Evaluation Criterion 1 Degree...

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Optimistic CC Performance Evaluation Criterion 1. Degree of Concurrency Less reshuffle High degree of concurrency 2. Resources used to recognize - Lock tables - Time stamps - Read/write sets - Complexity 3. Costs - Programming ease Scheduler Recognizes or Reshuffles history history
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Optimistic CC Performance General Comments Information needed by Concurrency Controllers Locks on database objects (System-R, Ingres, Rosenkrantz…) Time stamps on database objects (Thomsa, Reed) Time stamps on transactions (Kung, SDD-1, Schlageter, Bhargava…) Observations Time stamps mechanisms more fundamental than locking Time stamps carry more information Checking locks costs less than checking time stamps
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Optimistic CC Performance General Comments (cont.) When to synchronize First access to an object (Locking, pessimistic validation) At each access (question of granularity) After all accesses and before commitment (optimistic validation) Fundamental notions Rollback Identification of useless transactions Delaying commit point Semantics of transactions
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