DP-300 Plan and implement data platform resources Practice Question
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?
⚠ Common exam trap
Many exam-takers 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.
Answer choices
Why each option matters
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.
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 chains produce LCK_M_* waits, not RESOURCE_SEMAPHORE, which specifically tracks memory grant contention. It is tempting because blocking is a common cause of slowdowns, but the observed wait type rules it out; the issue is concurrent queries awaiting workspace memory.
- ✗
The disk IOPS limit is being reached, causing queuing.
Why it's wrong here
RESOURCE_SEMAPHORE waits indicate queries queuing for memory grants, not storage IOPS saturation, which surfaces as PAGEIOLATCH or WRITELOG waits. It is tempting because General Purpose tier storage is remote, but the wait type points to insufficient memory grant capacity under concurrency.
- ✗
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 waits occur when queries cannot obtain a memory grant because concurrent queries have consumed the available workspace memory. At 100 DTUs the General Purpose tier caps memory, so peak-hour concurrency triggers the intermittent slowdowns.
Go deeper
Related to this question
Learn chapter
Monitoring Database Performance with Azure Tools
Key term
Query Store
Query Store is a built-in SQL Server feature that captures and stores a history of query execution plans and performance data for easy monitoring and troubleshooting.
Key term
Azure SQL Performance Tuning
Azure SQL Performance Tuning is the process of optimizing the speed and efficiency of queries and database operations in Microsoft Azure SQL Database or SQL Managed Instance to reduce latency and improve throughput.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DP-300 practice question is part of Courseiva's free Microsoft certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DP-300 exam.