AWS DMS for Oracle Migration with Minimal Downtime and Rollback
A company wants to migrate a legacy Oracle database to AWS with minimal downtime. The database is 2 TB in size and runs on a single on-premises server. The company requires the ability to cut over quickly and roll back if needed. Which AWS service should be used?
Quick Answer
The answer is AWS Database Migration Service (DMS) with ongoing replication. This is the correct choice because DMS’s change data capture (CDC) feature continuously replicates transactions from the source Oracle database to an Amazon RDS for Oracle target, enabling a cutover with downtime measured in minutes rather than hours, while the ongoing replication stream also supports a clean rollback by simply stopping the replication and pointing applications back to the on-premises source. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding of hybrid migration patterns and the distinction between online (DMS with CDC) and offline methods—a common trap is choosing Snowball for a 2 TB database, but Snowball is offline and cannot meet the minimal downtime requirement, nor does it support rollback. Remember the memory tip: “DMS with CDC means you can cut and come back.”
⚠ Common exam trap
Candidates may think Snowball Edge is suitable for very large databases, but for minimal downtime requirements, an online replication service like DMS is necessary.
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
✓
AWS Database Migration Service (DMS) with ongoing replication from the source to an Amazon RDS for Oracle target.
AWS Database Migration Service (DMS) with ongoing replication enables continuous data replication from the on-premises Oracle database to Amazon RDS for Oracle, allowing minimal downtime during cutover. It also supports rollback by stopping replication and reverting to the source. Option A is incorrect because S3 Transfer Acceleration is for fast uploads to S3, not for database migration with replication. Option C is incorrect because AWS Schema Conversion Tool (SCT) handles schema conversion, not ongoing data replication. Option D is incorrect because AWS Snowball Edge is an offline data transfer device, which does not meet the minimal downtime requirement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use S3 Transfer Acceleration to upload the database dump directly to an EC2 instance.
Why it's wrong here
S3 Transfer Acceleration is designed for fast uploads to S3, not for database migration with minimal downtime; it cannot provide ongoing replication or rollback.
- ✓
AWS Database Migration Service (DMS) with ongoing replication from the source to an Amazon RDS for Oracle target.
Why this is correct
Correct. AWS DMS with ongoing replication enables near-zero downtime by continuously copying changes, and supports easy rollback by pausing or reversing replication.
- ✗
AWS Schema Conversion Tool (SCT) to convert the schema and then export the data to flat files for import.
Why it's wrong here
AWS SCT converts the schema but does not migrate data or support ongoing replication; it is used for schema conversion before DMS migration.
- ✗
AWS Snowball Edge to copy the database files and then restore on Amazon RDS.
Why it's wrong here
AWS Snowball Edge is an offline data transfer device that would require significant downtime to copy and restore data, and does not support ongoing replication or quick rollback.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
Go deeper
Related to this question
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Same concept, more angles
2 more ways this is tested on SAP-C02
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. Refer to the exhibit. A company is using AWS Migration Hub to track database migration tasks. The migration task for 'app-server-01' has failed. The progress update stream is 'DMS'. Which AWS service is most likely responsible for the migration failure?
hard- A.AWS Application Migration Service (CloudEndure)
- ✓ B.AWS Database Migration Service (DMS)
- C.AWS Server Migration Service (SMS)
- D.AWS CloudEndure Migration
Why B: The progress update stream 'DMS' indicates that the task is associated with AWS Database Migration Service (DMS). DMS is used for database migrations. AWS Application Migration Service (CloudEndure) would use a different stream. Server Migration Service (SMS) is deprecated. CloudEndure and SMS are for server migration, not database.
Variation 2. A migration engineer is setting up an AWS DMS task to migrate data from an on-premises Oracle database to Amazon RDS for PostgreSQL. The engineer attaches this IAM policy to the DMS service role. The DMS task fails with an error indicating insufficient privileges. What is the most likely cause?
hard- A.The policy does not allow the s3:ListBucket action for the S3 bucket
- B.The policy does not allow the dms:TestConnection action
- ✓ C.The policy does not allow the dms:CreateEndpoint action
- D.The policy does not allow the rds:ModifyDBInstance action
Why C: DMS needs permission to describe endpoints and test connections, which are not in the policy. The policy allows creating and starting tasks but not the prerequisite actions like creating endpoints. S3 access is correct if using S3 as a source/target, but the core issue is missing endpoint permissions.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SAP-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SAP-C02 exam.