An audit of a banking transactions system has found that on an earlier occasion, two joint holders of account A attempted simultaneous transfers of Rs. 10000 each from account A to account B. Both transactions read the same value, Rs. 11000, as the initial balance in A and were allowed to go through. B was credited Rs. 10000 twice. A was debited only once and ended up with a balance of Rs. 1000. Which of the following properties is/are certain to have been violated by the system?

Question

P and Q play chess frequently against each other. Of these matches, P has won 80% of the matches, drawn 15% of the matches, and lost 5% of the matches.
If they play 3 more matches, what is the probability of P winning exactly 2 of these 3 matches?

Answer 1

To solve this problem, we need to understand the ACID properties of database transactions, which are crucial to ensuring data integrity. Let's break it down according to each property to identify the violated one:

Atomicity: This property ensures that a series of operations within a transaction are all completed successfully, or none of them are. In the scenario, while both transactions were processed, each transaction by itself seems incomplete as B was credited) and only one debit occurred for A. However, lack of atomicity would typically result in no balance change for B or incorrect debits from A, which is not evident here. Therefore, Atomicity may not be the primary issue.
Consistency: Consistency ensures that a database transaction must transform the database from one valid state to another, following all rules and constraints (e.g., balance equations must hold). However, once adjustments are considered for a consistent rule check, the final states did not maintain valid constraints as B was credited incorrectly twice and A debited once violating expected invariant. However, given the context, it might be the lack of synchronization rather than Consistency principle being violated.
Isolation: This property ensures that transactions are performed independently without interference, maintaining individual transaction integrity. The problem with the described system is that concurrent transactions saw the initial balance as the same due to lack of isolation, causing them not to isolate processes resulting in defects. This violated the expected sequence and concurrency handling of separate transactions thus indicating violation of Isolation property. Hence, Isolation is certainly violated.
Durability: It ensures that once a transaction is committed, it remains so. If the results of the transaction are incorrect, we can't blame durability here as it pertains only to the permanent retention of data post-commit – current scenario did not highlight such retention issues post successful transaction.

Upon evaluation, the property that is certainly violated in the scenario is Isolation, as it fails to manage concurrent transactions independently, leading to incorrect balance updates.

Answer 2

To solve this problem, we need to understand the ACID properties of database transactions, which are crucial to ensuring data integrity. Let's break it down according to each property to identify the violated one:

Atomicity: This property ensures that a series of operations within a transaction are all completed successfully, or none of them are. In the scenario, while both transactions were processed, each transaction by itself seems incomplete as B was credited) and only one debit occurred for A. However, lack of atomicity would typically result in no balance change for B or incorrect debits from A, which is not evident here. Therefore, Atomicity may not be the primary issue.
Consistency: Consistency ensures that a database transaction must transform the database from one valid state to another, following all rules and constraints (e.g., balance equations must hold). However, once adjustments are considered for a consistent rule check, the final states did not maintain valid constraints as B was credited incorrectly twice and A debited once violating expected invariant. However, given the context, it might be the lack of synchronization rather than Consistency principle being violated.
Isolation: This property ensures that transactions are performed independently without interference, maintaining individual transaction integrity. The problem with the described system is that concurrent transactions saw the initial balance as the same due to lack of isolation, causing them not to isolate processes resulting in defects. This violated the expected sequence and concurrency handling of separate transactions thus indicating violation of Isolation property. Hence, Isolation is certainly violated.
Durability: It ensures that once a transaction is committed, it remains so. If the results of the transaction are incorrect, we can't blame durability here as it pertains only to the permanent retention of data post-commit – current scenario did not highlight such retention issues post successful transaction.

Upon evaluation, the property that is certainly violated in the scenario is Isolation, as it fails to manage concurrent transactions independently, leading to incorrect balance updates.

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The Correct Option is C

Solution and Explanation

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