The answer is that the database is experiencing memory pressure due to concurrent queries exceeding available memory. This is the most likely cause because a RESOURCE_SEMAPHORE wait in Azure SQL Database specifically indicates that a query is stalled waiting for a memory grant to execute, and on the General Purpose tier with 100 DTUs, the memory available for query execution is limited and shared with the buffer pool. During peak hours, when many concurrent queries request memory grants simultaneously, the pool can be exhausted, forcing subsequent queries to queue up—a classic symptom of memory pressure rather than CPU or I/O throttling. For the DP-300 exam, this scenario tests your ability to distinguish between different wait types: RESOURCE_SEMAPHORE always points to memory grant waits, not disk or CPU bottlenecks. A common trap is confusing this with RESOURCE_SEMAPHORE_QUERY_COMPILE, which is about compilation memory, but the plain RESOURCE_SEMAPHORE is about execution memory. Remember the mnemonic: "Semaphore says stop—your query needs a memory drop."
DP-300 Plan and implement data platform resources Practice Question
This DP-300 practice question tests your understanding of plan and implement data platform resources. 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.
You are troubleshooting a performance issue on Azure SQL Database. The database uses the General Purpose tier with 100 DTUs. Users report intermittent slowdowns during peak hours. Query Store shows frequent waits for RESOURCE_SEMAPHORE. 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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The database is experiencing memory pressure due to concurrent queries exceeding available memory.
RESOURCE_SEMAPHORE waits indicate that queries are waiting for memory grants to execute. In Azure SQL Database General Purpose tier with 100 DTUs, memory is shared between the buffer pool and query execution. During peak hours, concurrent queries can exhaust the available memory, forcing queries to wait for memory grants. This is a classic sign of memory pressure, not CPU or IO throttling.
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.
✗
There is a blocking chain due to unoptimized queries.
Why it's wrong here
Blocking causes LCK_M_ waits, not RESOURCE_SEMAPHORE.
✗
The disk IOPS limit is being reached, causing queuing.
Why it's wrong here
Disk IO waits manifest as PAGEIOLATCH or WRITELOG, not RESOURCE_SEMAPHORE.
✗
The DTU limit is being reached, causing CPU throttling.
Why it's wrong here
CPU throttling shows SOS_SCHEDULER_YIELD waits.
✓
The database is experiencing memory pressure due to concurrent queries exceeding available memory.
Why this is correct
RESOURCE_SEMAPHORE specifically indicates waiting for memory grant; common in under-provisioned tiers.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
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 often confuse DTU throttling (which affects CPU and IO) with memory pressure, but RESOURCE_SEMAPHORE is a memory-specific wait type that is not directly tied to DTU limits.
Trap categories for this question
Command / output trap
CPU throttling shows SOS_SCHEDULER_YIELD waits.
Detailed technical explanation
How to think about this question
RESOURCE_SEMAPHORE waits occur when the total memory grant requests exceed the available memory for query execution, which is capped by the 'max server memory' setting (approximately 80% of the tier's memory). In the General Purpose tier with 100 DTUs, the memory limit is roughly 1.56 GB, and concurrent large hash joins or sorts can quickly exhaust this. The wait type specifically tracks the time a query spends waiting for a memory grant from the resource semaphore, which is a SQLOS component that manages memory grants for query execution.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this DP-300 question in full detail.
Plan and implement data platform resources — This question tests Plan and implement data platform resources — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The database is experiencing memory pressure due to concurrent queries exceeding available memory. — RESOURCE_SEMAPHORE waits indicate that queries are waiting for memory grants to execute. In Azure SQL Database General Purpose tier with 100 DTUs, memory is shared between the buffer pool and query execution. During peak hours, concurrent queries can exhaust the available memory, forcing queries to wait for memory grants. This is a classic sign of memory pressure, not CPU or IO throttling.
What should I do if I get this DP-300 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: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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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