DP-300 Practice Question: Monitor, configure, and optimize database resources
You are monitoring an Azure SQL Database using sys.dm_db_wait_stats. You see a high percentage of WRITELOG waits. 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
✓
The transaction log is on a slow I/O subsystem.
A high percentage of WRITELOG waits indicates that transaction log writes are slow, often due to I/O latency on the log drive. Therefore, the most likely cause is a slow I/O subsystem for the transaction log (Option B). Option A is incorrect because tempdb allocation contention manifests as PAGELATCH waits. Option C is incorrect because blocking is represented by LCK_M_* waits. Option D is incorrect because CPU pressure shows SOS_SCHEDULER_YIELD 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.
- ✗
Tempdb has allocation contention.
Why it's wrong here
Tempdb contention shows PAGELATCH waits.
- ✓
The transaction log is on a slow I/O subsystem.
Why this is correct
WRITELOG waits directly relate to log write performance.
- ✗
Queries are blocked by locks.
Why it's wrong here
Blocking shows lock waits, not WRITELOG.
- ✗
CPU is under pressure.
Why it's wrong here
CPU pressure shows different wait types.
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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