DP-300 Practice Question: Monitor, configure, and optimize database resources
You are optimizing an Azure SQL Database that has a heavy workload of both reads and writes. The database has a clustered columnstore index on a large fact table. You notice that the index has high fragmentation and the performance of queries against this table is degrading. What should you do to improve performance?
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
✓
Rebuild the clustered columnstore index
Rebuilding the clustered columnstore index reduces fragmentation and improves query performance. Rebuilding is the recommended method to defragment a columnstore index. Option B is incorrect because increasing the service tier addresses performance issues related to IOPS but does not resolve fragmentation. Option C is incorrect because dropping and recreating the index is more disruptive and unnecessary; a rebuild achieves the same result with less overhead. Option D is incorrect because reorganize is not supported for columnstore indexes; only rebuild is.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Rebuild the clustered columnstore index
Why this is correct
Rebuild reduces fragmentation and improves scan performance.
- ✗
Increase the service tier to get more IOPS
Why it's wrong here
Increasing resources does not fix fragmentation.
- ✗
Drop and recreate the clustered columnstore index
Why it's wrong here
This works but is more disruptive than a rebuild.
- ✗
Reorganize the clustered columnstore index
Why it's wrong here
Reorganize is not supported on columnstore indexes; only rebuild is.
Visual reference
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Related to this question
Learn chapter
Overview of Azure Data Platform Options
Key term
Azure SQL Indexes
Structures in Azure SQL Database that speed up data retrieval by providing quick access paths to rows, similar to a book index.
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
Senior Network & Security Engineer · founder of Courseiva
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.