The correct answer is durability, the D in ACID, because it guarantees that once a transaction is committed, the data changes are permanently stored and will survive any subsequent system failure, such as a power outage or crash. This is achieved through mechanisms like the write-ahead log (WAL) and checkpoint processes, which ensure that all committed data is flushed to durable storage before the system acknowledges success. On the Microsoft Azure Data Fundamentals DP-900 exam, this property is frequently tested by contrasting it with atomicity (all-or-nothing execution) or isolation (concurrent transaction handling). A common trap is confusing durability with consistency—remember that durability is about persistence after commit, not data integrity rules. For a quick memory tip, think “D for Disk”—once committed, it’s written to disk and stays there, no matter what.
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 financial database system ensures that once a transaction is committed, the data changes are permanently stored and will survive any subsequent system failure, such as a power outage or crash. Which property of ACID transactions does this describe?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
D: Durability
D is correct because durability guarantees that once a transaction is committed, the changes persist permanently, even in the event of a system failure like a power outage or crash. In SQL Server, this is implemented via the write-ahead log (WAL) and checkpoint processes, ensuring committed data is flushed to disk before acknowledging success.
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.
✗
A: Atomicity
Why it's wrong here
Atomicity refers to the 'all-or-nothing' nature of a transaction; it does not guarantee permanence after a crash.
✗
B: Consistency
Why it's wrong here
Consistency ensures that a transaction brings the database from one valid state to another, respecting constraints and rules.
✗
C: Isolation
Why it's wrong here
Isolation deals with how concurrent transactions are protected from seeing each other's partial updates.
✓
D: Durability
Why this is correct
Durability ensures that once a transaction is committed, its effects are permanent and survive system failures.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse durability with atomicity, thinking 'permanent storage' relates to the all-or-nothing nature of a transaction, but atomicity only guarantees that partial changes are rolled back, not that committed data survives crashes.
Detailed technical explanation
How to think about this question
Under the hood, durability in SQL Server relies on the transaction log: before a commit is acknowledged, all log records for the transaction must be hardened to disk via a log flush. In a real-world scenario, if a power outage occurs immediately after commit, the database engine replays the log during recovery to reconstruct any data not yet written to the data files, ensuring no committed transaction is lost.
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: D: Durability — D is correct because durability guarantees that once a transaction is committed, the changes persist permanently, even in the event of a system failure like a power outage or crash. In SQL Server, this is implemented via the write-ahead log (WAL) and checkpoint processes, ensuring committed data is flushed to disk before acknowledging success.
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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Question Discussion
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