The answer is to increase the number of parallel threads in the DMS task settings. This configuration directly improves DMS migration performance under heavy write load because it allows the service to capture and apply changes from multiple table partitions or row changes concurrently, rather than being bottlenecked by a single thread processing the high volume of write operations sequentially. On the AWS Certified Database Specialty DBS-C01 exam, this question tests your understanding of DMS task tuning for source-side contention, often appearing alongside traps like suggesting a larger instance class or increasing the batch size, which address throughput but not the concurrency bottleneck. A common memory tip is to think of parallel threads as adding more checkout lanes to a busy store: when the source is flooded with writes, you need more workers, not just a faster cashier.
DBS-C01 Deployment and Migration Practice Question
This DBS-C01 practice question tests your understanding of deployment and migration. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
A company is using AWS Database Migration Service (AWS DMS) to migrate a 5 TB MySQL database to Amazon RDS for MySQL. The migration is taking longer than expected. The company notices that the source database has a high volume of write operations. Which configuration change would MOST likely improve the migration performance?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Increase the number of parallel threads in the DMS task settings.
Increasing the number of parallel threads in the DMS task settings allows AWS DMS to process multiple table partitions or row changes concurrently, which directly addresses the bottleneck caused by a high volume of write operations on the source. By default, DMS uses a single thread per table, but when the source is under heavy write load, parallel threads can capture and apply changes more efficiently, reducing the overall migration time.
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 number of parallel threads in the DMS task settings.
Why this is correct
Parallel threads allow concurrent loading of data, improving throughput for high-write workloads.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable Multi-AZ on the target RDS instance.
Why it's wrong here
Multi-AZ provides high availability, not performance improvement during migration.
✗
Use a smaller instance class for the replication instance to reduce cost.
Why it's wrong here
A smaller instance class may reduce performance, not improve it.
✗
Set the LOB mode to 'Full LOB mode'.
Why it's wrong here
Full LOB mode processes LOBs inline, which can slow migration; Limited LOB mode with appropriate max lob size is more efficient.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse increasing parallelism with enabling Multi-AZ or changing LOB settings, mistakenly thinking these options directly speed up migration, when in fact they address availability or data type handling, not throughput under heavy write load.
Detailed technical explanation
How to think about this question
AWS DMS parallel threads work by dividing the source table into segments based on primary key ranges or using the 'maxFullLoadSubTasks' setting to control concurrent full-load tasks. Under the hood, DMS uses Change Data Capture (CDC) to track ongoing writes, and increasing parallel apply threads (via the 'ParallelApplyThreads' and 'ParallelApplyBufferSize' settings) helps keep up with a high-write source by applying changes to the target in parallel, reducing lag. In real-world scenarios, tuning these parameters is critical when migrating busy OLTP databases where write throughput exceeds the default single-threaded apply rate.
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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Deployment and Migration — This question tests Deployment and Migration — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Increase the number of parallel threads in the DMS task settings. — Increasing the number of parallel threads in the DMS task settings allows AWS DMS to process multiple table partitions or row changes concurrently, which directly addresses the bottleneck caused by a high volume of write operations on the source. By default, DMS uses a single thread per table, but when the source is under heavy write load, parallel threads can capture and apply changes more efficiently, reducing the overall migration time.
What should I do if I get this DBS-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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