DP-300 Practice Question: Monitor, configure, and optimize database resources
You are monitoring an Azure SQL Database using dynamic management views (DMVs). You run a query against `sys.dm_exec_query_stats` to find the top 10 queries by total worker time. Several queries show high worker time but low logical reads. The database is not experiencing any blocking or deadlocks. What is the most likely cause of the high worker time?
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 queries are CPU-bound due to inefficient query plans.
High worker time (CPU time) with low logical reads indicates that the queries are CPU-bound rather than I/O-bound. Inefficient query plans, such as those with large hash joins, sorts, or non-sargable predicates, can cause excessive CPU consumption without generating many logical reads. Option A is incorrect because parameter sniffing typically leads to varying plan quality, but the consistent high worker time across multiple queries suggests a systematic plan efficiency issue, not necessarily parameter sniffing. Option B is incorrect because memory pressure would cause increased I/O activity (lazy writes) which is not observed with low logical reads. Option C is incorrect because transaction log writes are I/O operations and would not cause high worker time with low I/O.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The queries suffer from parameter sniffing leading to suboptimal plans.
Why it's wrong here
Parameter sniffing can cause suboptimal plans, but it usually results in varying performance rather than consistently high CPU with low I/O. The symptom here points to CPU-bound queries due to inefficient plan design.
- ✗
The queries are experiencing memory pressure causing excessive lazy writes.
Why it's wrong here
Memory pressure would manifest as high I/O (lazy writes) and increased logical reads, not low logical reads.
- ✗
The queries are waiting on transaction log writes.
Why it's wrong here
Transaction log writes are I/O operations and would not be a significant contributor to high worker time (CPU) with low I/O.
- ✓
The queries are CPU-bound due to inefficient query plans.
Why this is correct
Correct. High worker time with low logical reads is a classic sign of CPU-bound queries, often caused by inefficient query plans that perform heavy computations (e.g., complex joins, aggregations, or non-sargable predicates).
Go deeper
Related to this question
Learn chapter
Overview of Azure Data Platform Options
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
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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.