The answer is atomicity, because this ACID property guarantees that a database transaction is treated as a single, indivisible unit of work. In the fund transfer scenario, atomicity ensures that if the system crashes after debiting the first account but before crediting the second, the database engine automatically rolls back the partial debit using its transaction log, restoring the system to its original state. On the Microsoft Azure Data Fundamentals DP-900 exam, this concept tests your understanding of how Azure SQL Database or SQL Server handles transaction recovery, often appearing in questions about failure scenarios. A common trap is confusing atomicity with consistency—remember that atomicity is about “all or nothing” execution, not about data validity. For a quick memory tip, think of the word “atom” as something that cannot be split: a transaction either happens completely or not at all.
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 database system must ensure that when a transfer of funds between two accounts is processed, if the system crashes after debiting the first account but before crediting the second, the database automatically undoes the debit. This property is best described as:
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
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 the system crashes after debiting one account but before crediting the other, the database's transaction log records the partial changes, and during recovery, the database engine (e.g., SQL Server's ARIES recovery model) performs an automatic rollback of the uncommitted transaction, undoing the debit to maintain 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
Atomicity ensures that all operations in a transaction complete or none do; a crash triggers an automatic rollback, undoing the partial debit.
Clue confirmation
The clue words "best", "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Consistency
Why it's wrong here
Consistency ensures that data remains valid before and after a transaction, but it does not handle rollbacks of partial operations.
✗
Isolation
Why it's wrong here
Isolation ensures concurrent transactions do not interfere, but it does not address rollback on failure.
✗
Durability
Why it's wrong here
Durability guarantees that committed changes persist, but the scenario describes an uncommitted transaction being undone.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse atomicity with consistency, thinking that maintaining a correct total balance (consistency) is what undoes the debit, but atomicity is the property that specifically handles the rollback of incomplete transactions after a crash.
Trap categories for this question
Scenario analysis trap
Durability guarantees that committed changes persist, but the scenario describes an uncommitted transaction being undone.
Detailed technical explanation
How to think about this question
Under the hood, atomicity is implemented via a transaction log and a recovery mechanism. In SQL Server, the ARIES (Algorithms for Recovery and Isolation Exploiting Semantics) protocol uses a log sequence number (LSN) to track every change; during crash recovery, the database reads the log, identifies transactions without a commit record, and issues compensation log records (CLRs) to undo their effects. A real-world scenario is a banking transfer where the debit succeeds but the credit fails due to a power outage—atomicity ensures the debit is rolled back, preventing lost funds.
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 the system crashes after debiting one account but before crediting the other, the database's transaction log records the partial changes, and during recovery, the database engine (e.g., SQL Server's ARIES recovery model) performs an automatic rollback of the uncommitted transaction, undoing the debit to maintain 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.
Are there clue words in this question I should notice?
Yes — watch for: "best", "first". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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