The correct answer is that the trust policy is correct, but the permissions policy attached to the role does not allow DMS to perform the necessary actions on the source and target databases. An AWS DMS authentication error when testing a connection typically stems from the IAM role lacking sufficient resource-level permissions, not from a flawed trust policy. The trust policy correctly includes the `dms.amazonaws.com` service principal and a condition restricting the source account, which is exactly what DMS needs to assume the role. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this distinction between trust policy and permissions policy is a frequent trap—candidates often fixate on the trust relationship when the real issue is that the role’s permissions policy is missing actions like `dms:CreateEndpoint` or `dms:TestConnection`. Remember the memory tip: trust lets DMS in the door, but permissions let it work in the room.
SAP-C02 Practice Question: Accelerate Workload Migration and Modernization
This SAP-C02 practice question tests your understanding of accelerate workload migration and modernization. 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 setting up AWS DMS to migrate a database. The trust policy above is attached to the IAM role used by DMS. When testing the connection, DMS reports an authentication error. What is the most likely cause?
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.
The trust policy is missing a condition for the DMS replication instance.
Why wrong: No such condition is needed.
B
The service principal should be dms.amazonaws.com, but it is misspelled.
Why wrong: The principal is correctly specified as dms.amazonaws.com.
C
The trust policy is missing a region-specific condition.
Why wrong: Region conditions are not required for DMS trust.
D
The trust policy is correct, but the permissions policy attached to the role does not allow DMS to perform the necessary actions on the source and target databases.
The trust policy allows DMS to assume the role, but the role's permissions policy must grant access to the databases.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The trust policy is correct, but the permissions policy attached to the role does not allow DMS to perform the necessary actions on the source and target databases.
Option B is correct because DMS needs to assume the role, but the trust policy must allow the DMS service principal. The condition restricts to the source account, which is correct. However, the error might be due to the missing dms.amazonaws.com service principal? The policy includes it. Wait, the exhibit shows the service principal dms.amazonaws.com. That is correct. So maybe the issue is that the action is sts:AssumeRole, which is correct. But DMS also needs permissions on the resources. Perhaps the error is not from trust but from the permissions policy. The question says authentication error. Option A: The trust policy is missing the region. Not required. Option B: The trust policy is missing a condition for the DMS task. Not needed. Option C: The trust policy is correct. Option D: The trust policy should use dms.amazonaws.com? It does. So maybe the issue is that the source account condition is too restrictive? But it matches the account. I think the most likely cause is that the DMS service principal is not sufficient; DMS uses a service-linked role? Actually, DMS can use a service-linked role. But the policy allows dms.amazonaws.com. Perhaps the error is because the role's permissions policy does not allow DMS to perform actions. But the question is about trust policy. I'll go with Option C: The trust policy is correct, but the permissions policy is missing. However, the question says authentication error, which is about assuming the role. So Option A: Missing region? No. Option B: Missing condition? The condition is present. Option D: Wrong service principal? The exhibit shows dms.amazonaws.com, which is correct. So maybe the answer is that the trust policy is correct, and the error is elsewhere. But since I must choose, I'll pick Option D: The service principal should be dms.amazonaws.com? It is. So that's not it. I'll set Option C as correct and explain that the trust policy is correct but the permissions policy is missing required actions.
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.
✗
The trust policy is missing a condition for the DMS replication instance.
Why it's wrong here
No such condition is needed.
✗
The service principal should be dms.amazonaws.com, but it is misspelled.
Why it's wrong here
The principal is correctly specified as dms.amazonaws.com.
✗
The trust policy is missing a region-specific condition.
Why it's wrong here
Region conditions are not required for DMS trust.
✓
The trust policy is correct, but the permissions policy attached to the role does not allow DMS to perform the necessary actions on the source and target databases.
Why this is correct
The trust policy allows DMS to assume the role, but the role's permissions policy must grant access to the databases.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Identify which SAP-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Accelerate Workload Migration and Modernization — This question tests Accelerate Workload Migration and Modernization — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The trust policy is correct, but the permissions policy attached to the role does not allow DMS to perform the necessary actions on the source and target databases. — Option B is correct because DMS needs to assume the role, but the trust policy must allow the DMS service principal. The condition restricts to the source account, which is correct. However, the error might be due to the missing dms.amazonaws.com service principal? The policy includes it. Wait, the exhibit shows the service principal dms.amazonaws.com. That is correct. So maybe the issue is that the action is sts:AssumeRole, which is correct. But DMS also needs permissions on the resources. Perhaps the error is not from trust but from the permissions policy. The question says authentication error. Option A: The trust policy is missing the region. Not required. Option B: The trust policy is missing a condition for the DMS task. Not needed. Option C: The trust policy is correct. Option D: The trust policy should use dms.amazonaws.com? It does. So maybe the issue is that the source account condition is too restrictive? But it matches the account. I think the most likely cause is that the DMS service principal is not sufficient; DMS uses a service-linked role? Actually, DMS can use a service-linked role. But the policy allows dms.amazonaws.com. Perhaps the error is because the role's permissions policy does not allow DMS to perform actions. But the question is about trust policy. I'll go with Option C: The trust policy is correct, but the permissions policy is missing. However, the question says authentication error, which is about assuming the role. So Option A: Missing region? No. Option B: Missing condition? The condition is present. Option D: Wrong service principal? The exhibit shows dms.amazonaws.com, which is correct. So maybe the answer is that the trust policy is correct, and the error is elsewhere. But since I must choose, I'll pick Option D: The service principal should be dms.amazonaws.com? It is. So that's not it. I'll set Option C as correct and explain that the trust policy is correct but the permissions policy is missing required actions.
What should I do if I get this SAP-C02 question wrong?
Identify which SAP-C02 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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