Because it is a very fun game and if it is fun people like it
Answer:
There's a parking lot that is 600m² big. The lot must be able to hold at least 3 buses and 10 cars.
Each car takes up 6m² and each bus takes up 30m².
However, there can only be 60 vehicles in the lot at any given time.
The cost to park in the lot is $2.50 per day for cars and $7.50 per day for buses. The lot must make at least $75 each day to break even.
What is a possible car to bus ratio that would allow the lot to make profit?
The answer is a) It improves upon the two-phased commit by requiring that locks be acquired at the start of a transaction.
Reason: The 3PC is an extension or you can say developed from 2PC that avoids blocking of an operation. It just ensures that first n sites have intended to commit a transaction that means it acquires commits or locks before the start of any transaction to avoid any blocking.
Option b) is wrong as it does not allow coordination, it just let all the other sites do their transaction if any other site is blocked, so no coordination is there between sites that they will wait till their coordinator is corrected.
Option c) is wrong as lock operations are shared between other connections as when their coordinator fails, the new coordinator agrees to the old coordinator that they had shared locks before and they can start their transaction.
Option d) is wrong as option a) is correct.
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