The answer is atomicity. This ACID property ensures that a database transaction is treated as a single, indivisible unit of work, meaning it must either execute completely or not at all. In the bank transfer scenario, atomicity guarantees that if the system crashes after debiting Account A but before crediting Account B, the entire transaction is rolled back, reverting the partial debit to maintain data consistency. On the Microsoft Azure Data Fundamentals DP-900 exam, this concept tests your understanding of how Azure SQL Database or Cosmos DB handles transaction integrity, often appearing in scenario-based questions about fund transfers or inventory updates. A common trap is confusing atomicity with consistency—remember that atomicity focuses on the all-or-nothing execution of the transaction steps, not the validity of the data itself. For a quick memory tip, think of atomicity as "atom-sized": a transaction cannot be split into smaller parts; it either happens as one whole piece or gets erased entirely.
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 bank processes a fund transfer transaction. The system debits $100 from Account A and then credits $100 to Account B. If the system crashes after debiting Account A but before crediting Account B, the database automatically reverts the debit. Which ACID property ensures this behavior?
Correct - Atomicity guarantees that the transaction is all-or-nothing. The rollback of the debit upon crash is a direct result of atomicity enforcement.
B
Consistency
Why wrong: Incorrect - Consistency ensures that a transaction brings the database from one valid state to another, but it does not dictate that partial changes are rolled back on failure.
C
Isolation
Why wrong: Incorrect - Isolation ensures that concurrent transactions do not interfere with each other. It does not handle rollback of incomplete transactions.
D
Durability
Why wrong: Incorrect - Durability guarantees that committed changes persist even after a system failure. It does not apply to uncommitted transactions.
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 (e.g., a crash after debiting Account A but before crediting Account B), the entire transaction is rolled back, reverting any partial changes like the debit. This all-or-nothing behavior is the core of atomicity in database systems.
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
Correct - Atomicity guarantees that the transaction is all-or-nothing. The rollback of the debit upon crash is a direct result of atomicity enforcement.
Related concept
Read the scenario before looking for a memorised answer.
✗
Consistency
Why it's wrong here
Incorrect - Consistency ensures that a transaction brings the database from one valid state to another, but it does not dictate that partial changes are rolled back on failure.
✗
Isolation
Why it's wrong here
Incorrect - Isolation ensures that concurrent transactions do not interfere with each other. It does not handle rollback of incomplete transactions.
✗
Durability
Why it's wrong here
Incorrect - Durability guarantees that committed changes persist even after a system failure. It does not apply to uncommitted transactions.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse atomicity with consistency, thinking that 'keeping the database in a valid state' is what triggers the rollback, but it is actually atomicity that enforces the all-or-nothing rule for the transaction itself.
Detailed technical explanation
How to think about this question
Under the hood, atomicity is typically implemented using a transaction log (e.g., write-ahead logging in SQL Server or PostgreSQL). Before any data modification is written to disk, the before-image (old values) and after-image (new values) are recorded in the log. If a crash occurs, the recovery process (e.g., ARIES algorithm) reads the log and performs an UNDO of all uncommitted transactions, effectively reverting the debit. In a real-world scenario, this prevents 'missing money' where a debit is applied but the credit never completes, ensuring the bank's ledger remains balanced.
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 (e.g., a crash after debiting Account A but before crediting Account B), the entire transaction is rolled back, reverting any partial changes like the debit. This all-or-nothing behavior is the core of atomicity in database systems.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A bank processes a fund transfer that involves deducting money from one account and crediting it to another. The system ensures that both operations succeed together or, if any part fails, the entire transaction is rolled back, leaving both accounts unchanged. Which ACID property does this scenario primarily guarantee?
medium
A.Consistency
B.Isolation
C.Durability
✓ D.Atomicity
Why D: Atomicity ensures that a transaction is treated as a single, indivisible unit of work. In this fund transfer scenario, both the debit and credit operations must complete successfully, or the entire transaction is rolled back, leaving the accounts unchanged. This all-or-nothing behavior is the defining characteristic of atomicity in ACID transactions.
Variation 2. A bank processes online fund transfers. Each transaction must ensure that either both the debit from the sender's account and the credit to the receiver's account occur, or if any part fails, the entire transaction is rolled back. Which ACID property does this guarantee?
easy
✓ A.Atomicity
B.Consistency
C.Isolation
D.Durability
Why A: Atomicity ensures that a transaction is treated as a single, indivisible unit of work. In this fund transfer scenario, atomicity guarantees that both the debit and credit operations either complete successfully together or are fully rolled back if any part fails, preventing partial updates that could leave the system in an inconsistent state.
Last reviewed: Jun 11, 2026
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