The correct answer is to establish VPC peering or a VPN connection between the source and target VPCs, and configure security group rules to allow the DMS replication instance to reach the source Oracle database. This is required because AWS DMS operates within a VPC and needs direct network-layer connectivity to the source database; VPC peering or VPN bridges the two separate accounts’ networks, while security group rules act as the firewall to permit the specific DMS traffic. On the AWS Certified Database Specialty DBS-C01 exam, this question tests your understanding that DMS connectivity relies on network paths, not on AWS service endpoints or IAM roles for database authentication—a common trap is confusing IAM roles (used for S3 or target loading) with database credentials. Remember the memory tip: “Peer or VPN, then open the port; DMS needs a network path, not a role for the source.”
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 100 GB Oracle database to Amazon RDS for Oracle. They want to use AWS DMS. The source database is in a different AWS account. What is required to allow DMS to connect to the source?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Establish VPC peering or VPN between the source and target VPCs, and configure security group rules.
Option C is correct because DMS needs network connectivity via VPC peering or VPN, and the source security group must allow DMS. Option A is wrong because VPC endpoints are not needed for DMS to source. Option B is wrong because DMS does not use an S3 endpoint for source connectivity. Option D is wrong because DMS does not use an IAM role for database connectivity; it uses database credentials.
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.
✓
Establish VPC peering or VPN between the source and target VPCs, and configure security group rules.
Why this is correct
DMS requires network connectivity between the replication instance and the source database.
Related concept
Standard ACLs match source addresses.
✗
Assign an IAM role to the source database to allow DMS access.
Why it's wrong here
IAM roles are for AWS service permissions, not for database authentication.
✗
Configure an S3 VPC gateway endpoint for the source VPC.
Why it's wrong here
S3 endpoints are for S3 access, not for database connectivity.
✗
Create a VPC endpoint for DMS in the source account.
Why it's wrong here
VPC endpoints are for accessing AWS services, not for DMS connectivity to a database.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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: Establish VPC peering or VPN between the source and target VPCs, and configure security group rules. — Option C is correct because DMS needs network connectivity via VPC peering or VPN, and the source security group must allow DMS. Option A is wrong because VPC endpoints are not needed for DMS to source. Option B is wrong because DMS does not use an S3 endpoint for source connectivity. Option D is wrong because DMS does not use an IAM role for database connectivity; it uses database credentials.
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.
What is the key concept behind this question?
Standard ACLs match source addresses.
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Question Discussion
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