The answer is to increase the number of parallel apply threads on the DMS task. This is correct because when fixing DMS CDC lag, the bottleneck is often the apply phase, where DMS writes changes to the target Aurora PostgreSQL database. By increasing parallel apply threads, you allow DMS to commit multiple transactions concurrently, which directly accelerates the apply rate to match the 500 MB per minute of source redo logs. On the AWS Certified Database Specialty DBS-C01 exam, this question tests your understanding of DMS task tuning under high-volume CDC loads; a common trap is to confuse source-side tuning (like redo log size) with target-side throughput. Remember, redo logs are for Oracle, not for DMS speed. Memory tip: “Parallel applies push past the lag” — when CDC falls behind, think threads, not logs.
DBS-C01 Deployment and Migration Practice Question
This DBS-C01 practice question tests your understanding of deployment and migration. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 migrating a 10 TB Oracle database to Amazon Aurora PostgreSQL. The migration uses AWS DMS with CDC. After the full load, the CDC phase is falling behind by several minutes. The source Oracle database generates 500 MB of redo logs per minute. Which action will most likely improve CDC 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 apply threads on the DMS task
Option C is correct because increasing the DMS task's parallel apply threads can speed up the apply phase. Option A is wrong because increasing source redo log size does not affect DMS performance. Option B is wrong because disabling CDC is not a solution. Option D is wrong because reducing batch size would slow down processing.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Disable CDC and perform a full load only
Why it's wrong here
This would cause downtime and data loss.
✓
Increase the number of parallel apply threads on the DMS task
Why this is correct
More parallel apply threads can increase throughput for applying changes to the target.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
✗
Reduce the batch size in the DMS task settings
Why it's wrong here
Reducing batch size would decrease throughput, not improve it.
✗
Increase the source Oracle redo log size
Why it's wrong here
This does not directly affect DMS's ability to capture changes.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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. ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DBS-C01 ACL questions on filtering logic and placement.
Deployment and Migration — This question tests Deployment and Migration — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Increase the number of parallel apply threads on the DMS task — Option C is correct because increasing the DMS task's parallel apply threads can speed up the apply phase. Option A is wrong because increasing source redo log size does not affect DMS performance. Option B is wrong because disabling CDC is not a solution. Option D is wrong because reducing batch size would slow down processing.
What should I do if I get this DBS-C01 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DBS-C01 ACL questions on filtering logic and placement.
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?
Standard ACLs match source addresses.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is migrating a 5 TB Oracle database to Amazon Aurora MySQL using AWS DMS. The full load completes successfully, but the CDC phase is slow and the target Aurora cluster is consuming high CPU. The DMS instance type is dms.c4.2xlarge. Which change will most likely improve CDC performance?
hard
A.Increase the Aurora cluster's max_connections parameter
✓ B.Increase the number of parallel apply threads in the DMS task
C.Increase the DMS task's target storage allocation
D.Change the Aurora cluster to a larger instance class
Why B: Option D is correct because increasing the number of parallel apply threads can improve throughput, reducing CPU strain on Aurora. Option A is wrong because increasing max_connections may not help. Option B is wrong because Aurora auto-scales storage. Option C is wrong because DMS uses its own storage, not target storage.
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This DBS-C01 practice question is part of Courseiva's free Amazon Web Services 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 DBS-C01 exam.
Question Discussion
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