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DP-203 Practice Question: Secure, monitor, and optimize data storage and data processing

Your Azure Synapse Analytics dedicated SQL pool is experiencing performance degradation. Queries that previously completed in seconds now take minutes. You notice high queue wait times in sys.dm_pdw_exec_requests. What is the most likely cause?

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

Concurrency throttling due to insufficient resources

High queue wait times in sys.dm_pdw_exec_requests indicate that queries are waiting for resources, typically due to concurrency throttling when the number of concurrent queries exceeds the capacity of the current Service Level Objective (SLO). Option A (outdated statistics) can cause suboptimal execution plans but not necessarily queue waits. Option B (a single long-running query) would show high execution time for that query, not queue waits for others. Option D (data skew) leads to uneven distribution and slow data movement, not directly to queue waits.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • Outdated statistics

    Why it's wrong here

    Outdated stats cause suboptimal execution plans, not queue waits.

  • A single long-running query blocking others

    Why it's wrong here

    Blocking would show as lock waits, not queue waits.

  • Concurrency throttling due to insufficient resources

    Why this is correct

    Queue waits indicate queries are waiting for slots; increase SLO or optimize concurrency.

  • Data skew in distribution

    Why it's wrong here

    Data skew causes unbalanced processing, not queue waits.

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JA

Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

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