The correct answer is atomicity. Atomicity guarantees that a transaction is treated as an all-or-nothing unit, meaning every operation within it must complete successfully or none of them take effect. In the funds transfer scenario, the debit and credit are a single transaction; if the system crashes after the debit but before the credit, the database management system automatically performs a transaction rollback, undoing the debit to restore Account A’s original balance. On the Microsoft Azure Data Fundamentals DP-900 exam, this concept tests your understanding of how ACID properties ensure data integrity during failures, often appearing in scenario-based questions about banking or inventory systems. A common trap is confusing atomicity with durability—remember, atomicity is about the transaction’s indivisibility, not about saving data permanently. For a quick memory tip, think “atomicity = all or nothing, like an atom that cannot be split.”
DP-900 Describe core data concepts Practice Question
This DP-900 practice question tests your understanding of describe core data concepts. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 banking application processes a funds transfer transaction consisting of two steps: debit $100 from Account A and credit $100 to Account B. If the system crashes after debiting Account A but before crediting Account B, the database automatically reverts the debit, restoring Account A to its original balance. Which ACID property guarantees this behavior?
Correct. Atomicity guarantees the all-or-nothing nature of transactions. Since the debit is rolled back, the transaction is atomic.
B
Consistency
Why wrong: Consistency ensures that a transaction brings the database from one valid state to another, but it does not directly handle rollbacks on failure.
C
Isolation
Why wrong: Isolation ensures that concurrent transactions do not interfere with each other, but it does not address partial completion due to crashes.
D
Durability
Why wrong: Durability guarantees that once a transaction is committed, it persists even after a crash. In this scenario, the transaction was not committed, so durability is not applicable.
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. In this scenario, the debit and credit are part of one transaction; if the system crashes after the debit but before the credit, the database management system (DBMS) automatically rolls back the entire transaction, undoing the debit to restore Account A's original balance. This all-or-nothing behavior is the defining characteristic of atomicity.
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 the all-or-nothing nature of transactions. Since the debit is rolled back, the transaction is atomic.
Related concept
Read the scenario before looking for a memorised answer.
✗
Consistency
Why it's wrong here
Consistency ensures that a transaction brings the database from one valid state to another, but it does not directly handle rollbacks on failure.
✗
Isolation
Why it's wrong here
Isolation ensures that concurrent transactions do not interfere with each other, but it does not address partial completion due to crashes.
✗
Durability
Why it's wrong here
Durability guarantees that once a transaction is committed, it persists even after a crash. In this scenario, the transaction was not committed, so durability is not applicable.
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 'restoring the original balance' is about maintaining data rules, when in fact it is the rollback of an incomplete transaction that demonstrates atomicity.
Trap categories for this question
Scenario analysis trap
Durability guarantees that once a transaction is committed, it persists even after a crash. In this scenario, the transaction was not committed, so durability is not applicable.
Detailed technical explanation
How to think about this question
Under the hood, atomicity is typically implemented via a write-ahead log (WAL) or transaction log. Before any data page is modified, the DBMS records the old and new values in the log; if a crash occurs, the recovery process reads the log to undo (roll back) any uncommitted transactions. In SQL Server, this is managed by the transaction log and the recovery model (e.g., full, simple, bulk-logged), where incomplete transactions are rolled back during the undo phase of crash recovery.
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. In this scenario, the debit and credit are part of one transaction; if the system crashes after the debit but before the credit, the database management system (DBMS) automatically rolls back the entire transaction, undoing the debit to restore Account A's original balance. This all-or-nothing behavior is the defining characteristic of atomicity.
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. An e-commerce application processes customer orders. When an order is placed, the system must decrement the inventory count and process the payment. The application ensures that either both operations complete successfully or both are rolled back if any error occurs. Which database property does this guarantee?
medium
✓ A.Atomicity
B.Consistency
C.Isolation
D.Durability
Why A: Atomicity ensures that a transaction is treated as a single, indivisible unit of work: either all operations within it (decrement inventory and process payment) complete successfully, or none are applied. If any part fails, the database rolls back all changes, maintaining the 'all-or-nothing' guarantee. This is the core property described in the scenario.
Variation 2. A healthcare application stores patient medical history in a relational database. The system must ensure that after a transaction updates multiple records (e.g., diagnosis and medication), all changes are saved or none are saved. This property is best described as:
hard
✓ A.Atomicity
B.Consistency
C.Durability
D.Isolation
Why A: Atomicity ensures that a transaction is treated as a single, indivisible unit of work. In the context of a relational database storing patient medical history, if a transaction updates both the diagnosis and medication records, atomicity guarantees that either both updates are committed or both are rolled back, preventing partial updates that could leave the data in an inconsistent state.
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Question Discussion
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