Questions and Answers
What is the sequence of actions to modify a data item according to the text?
Lock (X), Write (X), Unlock (X)
In transaction processing, what does it mean for a transaction to be 'well-formed'?
A transaction is well-formed if it never locks a locked data item or tries to unlock an unlocked data item.
What access does a transaction have on a data item with an exclusive lock?
Read and Write
Can multiple transactions hold shared locks simultaneously on the same item?
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What is the purpose of upgrading a shared lock to an exclusive lock in some systems?
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If T1 locks data item A in exclusive mode, what should T2 do when it wants to lock A?
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What is the purpose of the locking method in transaction processing?
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What does a shared lock allow in transaction processing?
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When applying an Exclusive lock in transaction processing, what type of operation is allowed?
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What does Unlock(X) do in transaction processing?
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In transaction processing, what happens when a data item is under an Exclusive lock?
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What is the purpose of a Shared lock in transaction processing?
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What does an exclusive lock provide a transaction with?
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In the context of locking, what does it mean to upgrade a lock?
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Why is immediate unlocking after processing a data item considered incorrect?
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Which protocol requires all locking operations to precede the first unlock operation in a transaction?
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Why do the final results differ between serial and concurrent execution of transactions?
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Which action does Transaction T2 take when data item A is already locked by Transaction T1 in exclusive mode?
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