AWS DMS StartReplicationTask: Required IAM Permissions for Describe Endpoints and Connections
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.
Refer to the exhibit. An IAM policy is attached to a user who will manage AWS DMS tasks. When the user tries to start a replication task, they receive an access denied 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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The policy is missing permissions to describe endpoints and connections
Option C is correct because the DMS API requires that a user have permissions to describe endpoints and connections before starting a replication task. Even if the policy grants dms:StartReplicationTask, the service internally calls dms:DescribeEndpoints and dms:DescribeConnections to validate the source and target endpoints. Without those describe permissions, the API call fails with an access denied error, even though the start action itself is allowed.
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 policy does not allow rds:DescribeDBInstances
Why it's wrong here
The policy includes rds:DescribeDBInstances.
✗
The policy does not allow the dms:StartReplicationTask action
Why it's wrong here
The policy includes dms:StartReplicationTask, so this is not the issue.
✓
The policy is missing permissions to describe endpoints and connections
Why this is correct
To start a replication task, DMS needs to describe endpoints and connections; these actions are missing from the policy.
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.
✗
The policy does not allow dms:CreateReplicationTask
Why it's wrong here
The policy includes dms:CreateReplicationTask.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume the error is due to a missing start action (Option B) when the policy actually includes it, but they overlook that DMS requires additional describe permissions for endpoints and connections as a prerequisite to starting a task.
Detailed technical explanation
How to think about this question
Under the hood, when DMS starts a replication task, it performs a pre-flight validation that includes describing the source and target endpoints (dms:DescribeEndpoints) and their associated connections (dms:DescribeConnections) to ensure they are in a valid state. If the IAM policy lacks these describe permissions, the service returns an AccessDeniedException even if the start action is allowed. This is a common oversight because the error message may not explicitly list the missing describe actions, leading engineers to focus on the start action itself.
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 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 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: The policy is missing permissions to describe endpoints and connections — Option C is correct because the DMS API requires that a user have permissions to describe endpoints and connections before starting a replication task. Even if the policy grants dms:StartReplicationTask, the service internally calls dms:DescribeEndpoints and dms:DescribeConnections to validate the source and target endpoints. Without those describe permissions, the API call fails with an access denied error, even though the start action itself is allowed.
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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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 user has the IAM policy shown in the exhibit. When attempting to create a DMS replication task, they receive an authorization error. What is the most likely missing permission?
medium
A.ec2:DescribeSecurityGroups to allow network configuration
✓ B.dms:CreateEndpoint permission
C.s3:PutObject for the S3 bucket
D.logs:CreateLogGroup to enable logging
Why B: The user is attempting to create a DMS replication task, which requires the ability to create the underlying DMS resources. The error indicates a missing permission for the `dms:CreateEndpoint` action, as DMS replication tasks depend on source and target endpoints that must be created first. Without this permission, the API call to create the endpoint fails, resulting in an authorization error.
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Question Discussion
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