Podcast
Questions and Answers
What is the sequence of actions to modify a data item according to the text?
What is the sequence of actions to modify a data item according to the text?
- Lock (S), Write (X), Unlock (S)
- Lock (X), Read (S), Unlock (X)
- Lock (X), Write (X), Unlock (X) (correct)
- Lock (S), Read (S), Unlock (S)
In transaction processing, what does it mean for a transaction to be 'well-formed'?
In transaction processing, what does it mean for a transaction to be 'well-formed'?
- A transaction is well-formed if it constantly upgrades shared locks to exclusive locks.
- A transaction is well-formed if it holds all data items in exclusive mode throughout.
- A transaction is well-formed if it never locks a locked data item or tries to unlock an unlocked data item. (correct)
- A transaction is well-formed if it locks every data item it encounters.
What access does a transaction have on a data item with an exclusive lock?
What access does a transaction have on a data item with an exclusive lock?
- Read only
- No access
- Read and Write (correct)
- Write only
Can multiple transactions hold shared locks simultaneously on the same item?
Can multiple transactions hold shared locks simultaneously on the same item?
What is the purpose of upgrading a shared lock to an exclusive lock in some systems?
What is the purpose of upgrading a shared lock to an exclusive lock in some systems?
If T1 locks data item A in exclusive mode, what should T2 do when it wants to lock A?
If T1 locks data item A in exclusive mode, what should T2 do when it wants to lock A?
What is the purpose of the locking method in transaction processing?
What is the purpose of the locking method in transaction processing?
What does a shared lock allow in transaction processing?
What does a shared lock allow in transaction processing?
When applying an Exclusive lock in transaction processing, what type of operation is allowed?
When applying an Exclusive lock in transaction processing, what type of operation is allowed?
What does Unlock(X) do in transaction processing?
What does Unlock(X) do in transaction processing?
In transaction processing, what happens when a data item is under an Exclusive lock?
In transaction processing, what happens when a data item is under an Exclusive lock?
What is the purpose of a Shared lock in transaction processing?
What is the purpose of a Shared lock in transaction processing?
What does an exclusive lock provide a transaction with?
What does an exclusive lock provide a transaction with?
In the context of locking, what does it mean to upgrade a lock?
In the context of locking, what does it mean to upgrade a lock?
Why is immediate unlocking after processing a data item considered incorrect?
Why is immediate unlocking after processing a data item considered incorrect?
Which protocol requires all locking operations to precede the first unlock operation in a transaction?
Which protocol requires all locking operations to precede the first unlock operation in a transaction?
Why do the final results differ between serial and concurrent execution of transactions?
Why do the final results differ between serial and concurrent execution of transactions?
Which action does Transaction T2 take when data item A is already locked by Transaction T1 in exclusive mode?
Which action does Transaction T2 take when data item A is already locked by Transaction T1 in exclusive mode?
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