Question at position 28 A transaction is considered isolated when:it can only be run on one server.any changes in the database are not revealed to the user until the transaction is complete.users can see changes to tables before the transaction is complete.it runs in a vacuum.

Question

BlackTom AI · Accepted Answer

The question asks about the concept of isolation in transactions and provides four options to evaluate.
Option 1: 'it can only be run on one server.' This statement confuses isolation with a constraint about deployment or concurrency, but isolation is about visibility of changes during a transaction, not about where a transaction runs. Therefore, this option is inaccurate.
Option 2: 'any changes in the database are not revealed to the user until the transaction is complete.' This aligns with the core idea of isolation in ACID properties: the effects of an in-progress transaction should not be visible to other transactions or users until the transaction commits, ensuring consistency and preventing phenomena like dirty reads. This option correctly describes isolation.
Option 3: 'users can see changes to tables before the transaction is complete.' This directly contradicts the definition of isolation, which aims to prevent visibility of uncommitted changes. Hence this option is incorrect because it describes a lack of isolation (or a violation of it).
Option 4: 'it runs in a vacuum.' Figuratively describing a transaction as running in a vacuum is not a formal or accurate depiction of isolation in databases. It does not convey how or when changes become visible, making this option misleading and wrong.
In summary, Option 2 accurately expresses the essence of isolation by asserting that uncommitted changes are hidden until the transaction finishes, while Options 1, 3, and 4 mischaracterize or confuse the concept with deployment status, visibility, or metaphorical description.

Question at position 28 A transaction is considered isolated when:it can only be run on one server.any changes in the database are not revealed to the user until the transaction is complete.users can see changes to tables before the transaction is complete.it runs in a vacuum.单项选择题

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