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Deployment and Migration →hardMultiple ChoiceObjective-mapped

DBS-C01 Deployment and Migration Practice Question

This DBS-C01 practice question tests your understanding of deployment and migration. 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.

A company is migrating a 2 TB Oracle database running on an on-premises Linux server to Amazon RDS for Oracle. The migration must have minimal downtime and must be fully reversible if any issues arise. The DBA has configured AWS DMS with a full load and ongoing replication task. The full load completes successfully, and CDC is replicating changes. During the cutover window, the DBA stops the source database and promotes the target RDS instance. However, after cutover, the application team reports that some recent transactions are missing from the target database. The DBA confirms that the DMS task showed a 'healthy' status before stopping. Which action should the DBA take to resolve the issue and prevent recurrence?

A
Rebuild the entire migration using a native Oracle export/import tool.
Why wrong: This approach would cause significant downtime and does not prevent recurrence.
B
Increase the replication instance size to improve throughput.
Why wrong: Performance is not the issue; the issue is that the task did not capture all changes before stopping.
C
Restart the DMS task from the beginning to recapture the missing data.
Why wrong: Restarting does not recover the missing transactions because the source is already stopped.
D
Before stopping the source database, run the 'Stop task' command with the '--apply-immediately' option to ensure all cached changes are written to the target.
This ensures that all remaining CDC changes are applied before stopping.

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

✓

Before stopping the source database, run the 'Stop task' command with the '--apply-immediately' option to ensure all cached changes are written to the target.

The correct answer is D. In AWS DMS, after full load completes, ongoing replication (CDC) accumulates changes in a cache. To ensure no data loss during cutover, the DBA should stop the source database and then issue a 'Stop task' command with the '--apply-immediately' option (or use the 'Last Stop' job in the console) to flush all cached changes to the target before stopping the task. Option A (native export/import) would cause significant downtime and is unnecessary. Option B (increasing instance size) improves throughput but does not capture remaining cached changes. Option C (restarting from the beginning) would lose already migrated data and is not a targeted fix. Only option D directly addresses the issue of missing transactions by ensuring all CDC cached changes are applied before the task is stopped.

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.

✗
Rebuild the entire migration using a native Oracle export/import tool.
Why it's wrong here
This approach would cause significant downtime and does not prevent recurrence.
✗
Increase the replication instance size to improve throughput.
Why it's wrong here
Performance is not the issue; the issue is that the task did not capture all changes before stopping.
✗
Restart the DMS task from the beginning to recapture the missing data.
Why it's wrong here
Restarting does not recover the missing transactions because the source is already stopped.
✓
Before stopping the source database, run the 'Stop task' command with the '--apply-immediately' option to ensure all cached changes are written to the target.
Why this is correct
This ensures that all remaining CDC changes are applied before stopping.
Related concept
Standard ACLs match source addresses.

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.

Visual reference

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.

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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 — Standard ACLs match source addresses..

What is the correct answer to this question?

The correct answer is: Before stopping the source database, run the 'Stop task' command with the '--apply-immediately' option to ensure all cached changes are written to the target. — The correct answer is D. In AWS DMS, after full load completes, ongoing replication (CDC) accumulates changes in a cache. To ensure no data loss during cutover, the DBA should stop the source database and then issue a 'Stop task' command with the '--apply-immediately' option (or use the 'Last Stop' job in the console) to flush all cached changes to the target before stopping the task. Option A (native export/import) would cause significant downtime and is unnecessary. Option B (increasing instance size) improves throughput but does not capture remaining cached changes. Option C (restarting from the beginning) would lose already migrated data and is not a targeted fix. Only option D directly addresses the issue of missing transactions by ensuring all CDC cached changes are applied before the task is stopped.

What should I do if I get this DBS-C01 question wrong?

What is the key concept behind this question?

Standard ACLs match source addresses.

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