DP-300 Practice Question: Monitor, configure, and optimize database resources
You have a SQL Managed Instance that hosts a critical OLTP database. You notice that the average query wait time has increased significantly over the past hour. You need to identify the top resource waits. What should you use?
⚠ Common exam trap
Watch out — candidates often confuse performance metrics DMVs (like sys.dm_exec_query_stats) with wait statistics DMVs, or they assume Query Store Wait Stats is the primary diagnostic tool for real-time wait analysis, when sys.dm_os_wait_stats is the direct and authoritative source for identifying top resource waits.
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
✓
sys.dm_os_wait_stats
C is correct because sys.dm_os_wait_stats is the dynamic management view that aggregates wait statistics across all sessions in the SQL Server instance, including SQL Managed Instance. It provides cumulative wait times categorized by wait type (e.g., PAGEIOLATCH, LCK_M_S), making it the appropriate tool to identify top resource waits when average query wait time increases.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
sys.dm_exec_query_stats
Why it's wrong here
Shows execution statistics, not wait types.
- ✗
Query Store Wait Stats in SSMS
Why it's wrong here
Tracks waits per query but not aggregate top resource waits.
- ✓
sys.dm_os_wait_stats
Why this is correct
Provides cumulative wait statistics for all sessions.
- ✗
sys.dm_db_index_usage_stats
Why it's wrong here
Shows index usage, not wait statistics.
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Senior Network & Security Engineer · founder of Courseiva
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