hardMultiple Choice
FC0-U71 Practice Question: A database transaction that updates two accounts…
A database transaction that updates two accounts fails halfway due to a power outage. Which ACID property ensures that partial changes are undone?
⚠ Common exam trap
CompTIA often tests the distinction between atomicity (rollback of a failed transaction) and durability (persistence of committed data), so candidates mistakenly choose durability because they associate 'failure' with 'data loss' rather than 'partial update rollback'.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Atomicity
Atomicity ensures that a transaction is treated as a single, indivisible unit of work. If a power outage interrupts the transaction after updating one account but before updating the second, the database management system (DBMS) must roll back any partial changes to restore the original state. This 'all-or-nothing' property prevents incomplete transactions from leaving the database in an inconsistent state.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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Durability
Why it's wrong here
Durability guarantees committed transactions survive subsequent failures by persisting to non-volatile storage; it does not roll back uncommitted partial changes. It is tempting because durability also addresses power loss, but it would be correct if the question asked whether committed data survives a crash.
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Isolation
Why it's wrong here
Isolation governs concurrent transaction visibility, preventing dirty reads between simultaneous transactions; it does not reverse partial writes. It is tempting because isolation and atomicity both concern transaction integrity, but isolation would be the answer if the question asked about concurrent transactions interfering with each other.
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Consistency
Why it's wrong here
Consistency ensures a transaction moves the database between valid states, enforcing constraints and rules; it does not undo partial changes after failure. It is tempting because consistency sounds like data being kept correct, but it would be correct if the question concerned violating referential or schema constraints.
- ✓
Atomicity
Why this is correct
Atomicity treats the two account updates as a single indivisible unit, so if the power outage interrupts execution, the transaction rolls back and no partial debit or credit persists. This satisfies the stem's requirement that partial changes be undone.
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