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CSC 4402 20091116

CSC 4402 20091116 - A possible schedule S S can be executed...

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CSC 4402 11/16/2009 Page 1 of 1 Chapter 16 Focus on: Section 16.1 Section 16.6.3 Locking Basic assumptions 1) Every transaction T must request a lock in an appropriate mode on data item Q before T can access Q Lock(Q) Access(Q) Unlock(Q) 2) Two modes of lock: X – lock(exclusive) S – lock(shared) Back to the two-phase locking protocol……How many classes will they teach this in!?!?!
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Unformatted text preview: A possible schedule S: S can be executed to the end (no dead-locks) A legal schedule S under protocol P: S is a possible schedule and each transaction in S follows the protocol P Figure 1 – Schedule subsets Focus on deadlock detection – we emphasize the use of locking. If locks are used deadlocks cannot be prevented, so we must be able to detect them....
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