DP-300 Practice Question: Monitor, configure, and optimize database resources
You are managing an Azure SQL Database that has Automatic Tuning enabled. You receive an alert that a query plan regression was detected and a plan correction was automatically applied. You want to verify the performance improvement. What should you use?
⚠ Common exam trap
DP-300 often tests the misconception that Azure Monitor or the tuning log provides the detailed before/after performance evidence, when in fact Query Store is the only feature that retains historical plan and runtime data.
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
✓
Query the Query Store to compare query performance before and after the plan change.
Query Store is the built-in feature that captures query plan history and runtime statistics over time, so it can directly compare a query's performance before and after an automatic plan correction was applied. Automatic tuning relies on Query Store as its data source, and the 'Automatic Tuning' recommendation history is also surfaced through Query Store views such as sys.query_store_plan and sys.query_store_runtime_stats. This makes Query Store the authoritative place to verify the improvement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use sys.dm_exec_query_stats to view current performance.
Why it's wrong here
Query stats aggregate current execution metrics but retain no history of the regressed plan or the forced plan, so the before-and-after comparison cannot be reconstructed. It is tempting because it is the standard tool for tuning live queries, and would be correct when investigating which statements currently consume the most resources.
- ✗
Review the Azure Monitor alert details.
Why it's wrong here
The alert records only that regression was detected and correction applied; it carries no query-level performance data, so improvement cannot be measured. Reviewing alert details is tempting because it confirms the tuning event fired, and would be right when validating that Automatic Tuning is active and notifying correctly.
- ✓
Query the Query Store to compare query performance before and after the plan change.
Why this is correct
Query Store persists historical execution plans and runtime statistics, letting you compare a query's performance before and after the automatic plan correction. This directly satisfies the requirement to verify improvement, since the regression and forced plan are both recorded with their respective metrics.
- ✗
Check the automatic tuning log in the Azure portal.
Why it's wrong here
The automatic tuning log records recommendations and actions such as plan correction, but it does not quantify the resulting performance change. Query Store captures plan-level runtime statistics, letting you compare the regressed and corrected plans directly. Verifying improvement therefore requires Query Store's runtime data, not the tuning log.
Go deeper
Related to this question
Learn chapter
Managing Identity and Access for Azure SQL
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.
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.
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Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Microsoft exam blueprint
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