Quick Answer
The answer is atomicity, the ACID property that guarantees a transaction is treated as an all-or-nothing operation. When a power outage interrupts a transaction after updating one account but before the second, atomicity forces the database management system to perform a transaction rollback, undoing any partial changes to restore the database to its original, consistent state. On the CompTIA ITF+ FC0-U61 exam, this concept tests your understanding of how databases maintain integrity during failures—a common trap is confusing atomicity with durability, which deals with saving completed transactions permanently. A helpful memory tip is to think of atomicity as “indivisible,” like a single atom: if the transaction cannot finish completely, it must be rolled back entirely, leaving no trace of the partial work.
This FC0-U61 practice question tests your understanding of database fundamentals. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A database transaction that updates two accounts fails halfway due to a power outage. Which ACID property ensures that partial changes are undone?
Durability
Why wrong: Durability ensures committed changes persist, not rollback of uncommitted ones.
Isolation
Why wrong: Isolation prevents concurrent transactions from interfering, not rollback.
Consistency
Why wrong: Consistency ensures data validity, but rollback is handled by atomicity.
Atomicity
Atomicity ensures all or nothing; partial changes are rolled back.
Answer choices
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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Durability
Why it's wrong here
Durability ensures committed changes persist, not rollback of uncommitted ones.
Isolation
Why it's wrong here
Isolation prevents concurrent transactions from interfering, not rollback.
Consistency
Why it's wrong here
Consistency ensures data validity, but rollback is handled by atomicity.
Atomicity
Why this is correct
Atomicity ensures all or nothing; partial changes are rolled back.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
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'.
Detailed technical explanation
Under the hood, atomicity is typically implemented via a write-ahead log (WAL) or undo log. Before any data modification is written to the actual database pages, the DBMS records the old values in the log. If a crash occurs, the recovery process reads the log during restart and applies undo operations for any transaction that did not commit, effectively rolling back partial changes. In PostgreSQL, this is managed by the WAL and the transaction commit log (clog); in MySQL/InnoDB, the undo tablespace stores rollback segments for this purpose.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the FC0-U61 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
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FAQ
Database Fundamentals — This question tests Database Fundamentals — Read the scenario before looking for a memorised answer..
The correct answer is: 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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
This FC0-U61 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the FC0-U61 exam.
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