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    Question

    Which of the following is an essential feature of the ACID

    properties of a transaction in a database system?
    A Transactions are automatically rolled back if they fail. Correct Answer Incorrect Answer
    B Transactions are processed sequentially to ensure consistency Correct Answer Incorrect Answer
    C Transactions can only be executed by one user at a time. Correct Answer Incorrect Answer
    D Transactions are allowed to interfere with each other if they do not conflict Correct Answer Incorrect Answer
    E Transactions are atomic, meaning they are either fully completed or fully rolled back. Correct Answer Incorrect Answer

    Solution

    The ACID properties of a database transaction ensure reliable processing of transactions, even in the presence of power outages, crashes, or other failures. These properties are:

    • Atomicity : This ensures that a transaction is treated as a single "unit," which either completes entirely or has no effect at all (it is rolled back). This prevents partial updates that could lead to inconsistent database states.
    • Consistency : A transaction takes the database from one consistent state to another.
    • Isolation : Transactions are isolated from each other to prevent interference.
    • Durability : Once a transaction is committed, its effects are permanent, even in the case of a system crash.
    Thus, atomicity ensures that the transaction is "all or nothing" and prevents any intermediate state from being visible to other transactions. Why other options are incorrect:
    • A is incorrect because automatic rollback is part of atomicity , but it is not the defining feature.
    • B is incorrect because while transactions must be consistent, they do not need to be processed sequentially.
    • C is incorrect because transactions can be executed concurrently as long as they are isolated and do not conflict.
    • D is incorrect because transaction isolation is crucial for maintaining data integrity, and transactions should not interfere with each other unless they are properly synchronized.

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