The answer is atomicity, the ACID property that enforces all-or-nothing transaction processing. This is correct because atomicity treats a transaction as a single, indivisible unit of work: if any part of the transaction fails, the entire operation is rolled back, leaving the database unchanged, and no partial changes are ever saved. On the Microsoft Azure Data Fundamentals DP-900 exam, this concept tests your understanding of how Azure SQL Database or Cosmos DB guarantees data integrity during failures, often appearing in scenario-based questions where a system crash occurs mid-transaction. A common trap is confusing atomicity with consistency—remember that atomicity focuses on the transaction’s completeness, not the validity of data. For a quick memory tip, think “all or nothing, like a light switch: it’s either fully on or fully off, never dimmed.”
DP-900 Describe core data concepts Practice Question
This DP-900 practice question tests your understanding of describe core data concepts. 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 system ensures that a transaction either completes fully and all changes are applied, or it is completely rolled back and no partial changes are saved. Which property of ACID transactions does this describe?
Atomicity guarantees that all operations within a transaction are completed successfully or none are applied. This 'all or nothing' property prevents partial updates.
B
Consistency
Why wrong: Consistency ensures that a transaction transforms the database from one valid state to another, respecting all defined rules (e.g., constraints). It does not directly address the all-or-nothing behavior.
C
Isolation
Why wrong: Isolation ensures that concurrent transactions do not see each other's intermediate states. It deals with concurrency, not transaction completeness.
D
Durability
Why wrong: Durability guarantees that once a transaction is committed, its changes are permanent and survive system failures. It is about persistence, not atomicity.
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 any part of the transaction fails, the entire transaction is rolled back, leaving the database in its original state. This property guarantees that no partial changes are saved, which directly matches the description in the question.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Atomicity
Why this is correct
Atomicity guarantees that all operations within a transaction are completed successfully or none are applied. This 'all or nothing' property prevents partial updates.
Related concept
Read the scenario before looking for a memorised answer.
✗
Consistency
Why it's wrong here
Consistency ensures that a transaction transforms the database from one valid state to another, respecting all defined rules (e.g., constraints). It does not directly address the all-or-nothing behavior.
✗
Isolation
Why it's wrong here
Isolation ensures that concurrent transactions do not see each other's intermediate states. It deals with concurrency, not transaction completeness.
✗
Durability
Why it's wrong here
Durability guarantees that once a transaction is committed, its changes are permanent and survive system failures. It is about persistence, not atomicity.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Microsoft often tests the distinction between atomicity and consistency by describing a scenario where a transaction either fully applies or fully rolls back, leading candidates to mistakenly choose consistency because they associate 'valid state' with 'complete execution'.
Detailed technical explanation
How to think about this question
Under the hood, atomicity is typically implemented using a transaction log (e.g., the transaction log in SQL Server or the WAL in PostgreSQL). Before any data page is modified, the 'before' and 'after' images of the change are written to the log. If a failure occurs before the commit record is written, the recovery process uses the log to undo any partially written changes, ensuring atomic rollback. In distributed systems, atomicity across multiple nodes is achieved via two-phase commit (2PC) or the XA standard, which coordinates prepare and commit phases to prevent partial commits.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this DP-900 question in full detail.
Describe core data concepts — This question tests Describe core data concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Atomicity — Atomicity ensures that a transaction is treated as a single, indivisible unit of work. If any part of the transaction fails, the entire transaction is rolled back, leaving the database in its original state. This property guarantees that no partial changes are saved, which directly matches the description in the question.
What should I do if I get this DP-900 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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