Quick Answer
The answer is an insufficient memory grant, which forces batch mode execution to fall back to row mode when using a columnstore index in Azure SQL Database. Batch mode requires a larger memory grant than row mode because it processes rows in batches, and if the query optimizer estimates too little memory—often due to outdated statistics or complex joins—the engine cannot allocate the needed resources, triggering a fallback to row mode. On the DP-300 exam, this tests your understanding of how memory grants directly affect batch mode eligibility, a common trap where candidates assume compatibility level or index type is the issue. Remember that columnstore indexes enable batch mode by default, but without enough memory, the query degrades to row mode. Memory tip: think of batch mode as a fuel-hungry engine—without enough fuel (memory), it stalls and reverts to row mode.
This DP-300 practice question tests your understanding of monitor, configure, and optimize database resources. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
You are tuning a query in Azure SQL Database that uses a nonclustered columnstore index. The query is supposed to use batch mode execution but shows row mode. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
The query does not have enough memory grant
Insufficient memory grant forces row mode execution.
The database compatibility level is below 130
Why wrong: Compatibility level 130+ supports batch mode.
The index is defined with a filter predicate
Why wrong: Filtered columnstore indexes still support batch mode.
The query hint MAXDOP 1 is used
Why wrong: Batch mode works with single DOP.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The query does not have enough memory grant
Option D is correct because batch mode requires sufficient memory grant; if the query is memory-constrained, it may fall back to row mode. Option A is wrong because compatibility level 130 or higher supports batch mode. Option B is wrong because columnstore indexes support batch mode by default. Option C is wrong because MAXDOP setting does not disable batch mode.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The query does not have enough memory grant
Why this is correct
Insufficient memory grant forces row mode execution.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
The database compatibility level is below 130
Why it's wrong here
Compatibility level 130+ supports batch mode.
The index is defined with a filter predicate
Why it's wrong here
Filtered columnstore indexes still support batch mode.
The query hint MAXDOP 1 is used
Why it's wrong here
Batch mode works with single DOP.
Common exam traps
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
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. NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DP-300 NAT questions on configuration and troubleshooting.
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FAQ
Monitor, configure, and optimize database resources — This question tests Monitor, configure, and optimize database resources — Static NAT maps one inside address to one outside address..
The correct answer is: The query does not have enough memory grant — Option D is correct because batch mode requires sufficient memory grant; if the query is memory-constrained, it may fall back to row mode. Option A is wrong because compatibility level 130 or higher supports batch mode. Option B is wrong because columnstore indexes support batch mode by default. Option C is wrong because MAXDOP setting does not disable batch mode.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related DP-300 NAT questions on configuration and troubleshooting.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 21, 2026
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