The answer is to change the database to use read committed snapshot isolation (RCSI) and modify the procedure to use read committed. This is correct because the `LCK_M_IX` waits are caused by the serializable isolation level, which places aggressive range locks on the `Orders` table during concurrent `UPDATE` operations, blocking other transactions. By switching to RCSI, you enable statement-level row versioning, which allows readers to see a consistent snapshot without waiting for writers, directly eliminating the blocking bottleneck without schema or hardware changes. On the DP-300 exam, this scenario tests your understanding of how isolation levels impact concurrency in Azure SQL Database, often appearing as a trap where candidates mistakenly try to add indexes or scale vCores. The key insight is that serializable is overkill for order processing; RCSI with read committed provides the right balance of consistency and performance. Memory tip: "Serializable locks the range, RCSI removes the pain."
DP-300 Practice Question: Monitor, configure, and optimize database resources
This DP-300 practice question tests your understanding of monitor, configure, and optimize database resources. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
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?
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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often 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.
Detailed technical explanation
How to think about this question
Under serializable isolation, SQL Server acquires range locks (key-range locks) to prevent phantoms, which can escalate to blocking when multiple transactions try to update overlapping ranges. RCSI uses tempdb to store row versions, allowing readers to see a consistent snapshot without acquiring shared locks, thus eliminating `LCK_M_IX` waits for read operations. However, writers still use pessimistic locking; the key is that the procedure's `UPDATE` will only block other writers on the same rows, not readers, and the read committed isolation (with RCSI) avoids the range locks that serializable imposes.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this DP-300 question in full detail.
Monitor, configure, and optimize database resources — This question tests Monitor, configure, and optimize database resources — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 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.
What should I do if I get this DP-300 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.