← DBS-C01·Amazon Web Services

Question 1,126 of 1,730

Deployment and Migration →hardMultiple ChoiceObjective-mapped

AWS DMS Migration Performance Tuning

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 2 TB Oracle database to Amazon Aurora PostgreSQL using AWS DMS. The migration is taking longer than expected, and the ongoing replication lag is increasing. Which action would MOST likely improve the migration speed?

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.

A
Enable parallel load on the DMS task.
Why wrong: Parallel load is for full load, not ongoing replication.
B
Decrease the DMS task's batch size and commit interval.
Why wrong: Smaller batches can increase overhead, not improve speed.
C
Increase the DMS replication instance size.
More resources improve replication performance.
D
Disable the DMS task's logging to reduce overhead.
Why wrong: Disabling logging is not recommended and may cause data loss.

Full breakdown with real-world context →

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

✓

Increase the DMS replication instance size.

Increasing the replication instance size (Option C) directly addresses the root cause of slow migration and increasing replication lag: insufficient compute or network resources on the DMS instance. A larger instance provides more CPU, memory, and network bandwidth, enabling faster full-load processing and more efficient ongoing replication. This is the most effective action when the instance is resource-constrained, which is common with a 2 TB database.

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.

✗
Enable parallel load on the DMS task.
Why it's wrong here
Parallel load is for full load, not ongoing replication.
✗
Decrease the DMS task's batch size and commit interval.
Why it's wrong here
Smaller batches can increase overhead, not improve speed.
✓
Increase the DMS replication instance size.
Why this is correct
More resources improve replication performance.
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.
✗
Disable the DMS task's logging to reduce overhead.
Why it's wrong here
Disabling logging is not recommended and may cause data loss.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often assume tuning batch sizes or parallel load settings will fix performance issues, but the question explicitly states the migration is taking longer than expected and replication lag is increasing, which points to an under-provisioned replication instance rather than suboptimal task configuration.

Detailed technical explanation

How to think about this question

Under the hood, AWS DMS replication instances have fixed limits on vCPU, memory, and network throughput (e.g., a dms.r5.large has 2 vCPUs and 16 GiB memory, while a dms.r5.4xlarge has 16 vCPUs and 128 GiB memory). For a 2 TB Oracle source, the full-load phase requires significant I/O and memory to cache table data, and ongoing CDC replication demands sustained network bandwidth to capture and apply changes. Increasing the instance size also increases the maximum number of concurrent connections and the size of the cache for transaction logs, directly reducing lag.

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

An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.

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.

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FAQ

Questions learners often ask

What does this DBS-C01 question test?

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 DMS replication instance size. — Increasing the replication instance size (Option C) directly addresses the root cause of slow migration and increasing replication lag: insufficient compute or network resources on the DMS instance. A larger instance provides more CPU, memory, and network bandwidth, enabling faster full-load processing and more efficient ongoing replication. This is the most effective action when the instance is resource-constrained, which is common with a 2 TB database.

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.

About these practice questions

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Same concept, more angles

2 more ways this is tested on DBS-C01

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 3 TB on-premises Oracle database to Amazon Aurora PostgreSQL. The source database runs Oracle 12c on a Linux server with a 1 Gbps network connection to AWS via Direct Connect. The migration must have minimal downtime and be completed within a 2-day window. The database is heavily used during business hours (9 AM - 5 PM) and has low activity overnight. The company has a test environment on AWS already. The migration team plans to use AWS DMS with CDC for ongoing replication. They also plan to use AWS SCT for schema conversion. They start the migration on a Friday evening. On Saturday morning, the CDC replication lag is increasing, and the target Aurora instance is struggling to keep up. The team notices that the source database has a high number of write transactions even during the weekend, and the DMS replication instance is a small instance type. Which action should the team take to complete the migration on time?

hard

A.Reduce the number of tables being migrated to lower the load.
✓ B.Upgrade the DMS replication instance to a larger size to increase throughput.
C.Pause the migration and restart it on Monday during low activity.
D.Switch to use AWS Snowball to transfer data and bypass DMS.

Why B: Option B is correct because upgrading the DMS replication instance increases its capacity to handle high write volume. Option A is wrong because it doesn't address the bottleneck. Option C is wrong because it adds complexity and may not help. Option D is wrong because it doesn't solve the replication lag.

Variation 2. A company is migrating a PostgreSQL database to Amazon Aurora PostgreSQL. They have set up AWS DMS with change data capture (CDC). However, after the initial load, the CDC replication is experiencing high latency. What is the MOST likely cause?

medium

A.The target Aurora instance has insufficient storage.
B.The DMS instance is using an older engine version.
✓ C.The source database has large transactions that are not committed quickly.
D.The network bandwidth is too low.

Why C: Large uncommitted transactions on the source database cause DMS CDC to buffer changes until the transaction commits, leading to high latency. DMS must wait for the commit record before applying changes to the target Aurora instance, and during this time, CDC replication stalls, accumulating a backlog of changes.

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