DP-300 Practice Question: Monitor, configure, and optimize database resources
You are the database administrator for a large e-commerce company. The production Azure SQL Database (Business Critical, 16 vCores) hosts the order processing system. Recently, users report that order submissions are slow during peak hours. You examine the wait statistics and find that `LCK_M_IX` waits are the top wait type. You also notice that the stored procedure `usp_PlaceOrder` performs an `UPDATE` on the `Orders` table, and there is a high volume of concurrent transactions. The table has a clustered index on `OrderID` and a nonclustered index on `CustomerID`. The procedure uses serializable isolation level. Which action will most effectively reduce the blocking?
⚠ Common exam trap
Test-takers frequently assume scaling up hardware (Option A) or adding indexes (Option C) will fix blocking, when the root cause is the isolation level's locking behavior, which requires a concurrency model change like RCSI.
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
✓
Change the database to use read committed snapshot isolation (RCSI) and modify the procedure to use read committed.
The primary issue is blocking caused by `LCK_M_IX` waits under the serializable isolation level, which holds range locks and prevents concurrent updates. Changing to read committed snapshot isolation (RCSI) and using read committed eliminates these locks by providing statement-level row versioning, allowing concurrent transactions to read without blocking writers. This directly addresses the high volume of concurrent `UPDATE` operations without requiring schema or hardware changes.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Increase the vCore count to 24.
Why it's wrong here
More compute does not reduce blocking.
- ✗
Convert the Orders table to a memory-optimized table.
Why it's wrong here
Memory-optimized tables require application changes and are complex.
- ✗
Add a nonclustered index on the Status column of the Orders table.
Why it's wrong here
Index on Status does not reduce locking conflicts.
- ✓
Change the database to use read committed snapshot isolation (RCSI) and modify the procedure to use read committed.
Why this is correct
RCSI uses row versioning to avoid locks.
Go deeper
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.