How to Achieve Minimal Downtime Using AWS DMS with Ongoing Replication
A company wants to migrate a 500 GB SQL Server database to Amazon RDS for SQL Server with the least amount of downtime. The on-premises network has a 1 Gbps connection to AWS. Which approach should be used?
Quick Answer
The answer is to use AWS DMS with ongoing replication, as this approach enables minimal downtime database migration by continuously synchronizing changes from the on-premises SQL Server to the target Amazon RDS for SQL Server until the final cutover. AWS DMS captures ongoing transactions from the source using change data capture (CDC), allowing the target to remain nearly in sync, so the actual downtime window is reduced to just the seconds needed to redirect traffic. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding of migration strategies under strict uptime requirements, often contrasting DMS with native backup/restore (which incurs full downtime during restore) or offline methods like Snowball. A common trap is choosing a simpler but disruptive option because it seems familiar, so remember that “ongoing replication” is the key phrase for near-zero downtime. Memory tip: think “DMS syncs, downtime shrinks.”
⚠ Common exam trap
Many candidates choose native backup/restore (Option D) thinking it is the fastest because it is familiar, but they overlook that it requires a full backup (causing downtime) and lacks ongoing replication, whereas DMS with CDC provides near-zero downtime by replicating changes continuously.
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
✓
Use AWS DMS with ongoing replication from on-premises to RDS
AWS DMS with ongoing replication (change data capture, CDC) allows you to perform a full load of the 500 GB database while continuously replicating ongoing changes from the on-premises SQL Server to Amazon RDS for SQL Server. This minimizes downtime to a brief cutover window when you stop writes on the source and redirect traffic to the target. The 1 Gbps connection is sufficient for the initial load and ongoing replication, making this the most effective approach for minimal downtime.
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 AWS DMS with ongoing replication from on-premises to RDS
Why this is correct
DMS with CDC minimizes downtime by synchronizing changes until cutover.
- ✗
Use AWS Snowball to transfer the database backup, then restore to RDS
Why it's wrong here
Snowball adds shipping delay, increasing downtime.
- ✗
Copy database files to S3 and then use RDS import
Why it's wrong here
RDS does not support direct import from .bak files via S3 without a native restore.
- ✗
Use native SQL Server backup to S3, then restore to RDS
Why it's wrong here
This method requires downtime during backup and restore, and does not support ongoing replication.
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Same concept, more angles
3 more ways this is tested on DBS-C01
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 company wants to migrate a 200 GB SQL Server database to Amazon RDS for SQL Server with minimal downtime. The database is used by a critical application. Which service should be used for the migration?
easy- A.AWS Schema Conversion Tool (SCT).
- ✓ B.AWS Database Migration Service (DMS).
- C.SQL Server Import and Export Wizard.
- D.SQL Server Management Studio (SSMS) backup and restore.
Why B: AWS DMS is the correct choice because it supports ongoing replication (change data capture) from a SQL Server source to an Amazon RDS for SQL Server target, enabling a migration with minimal downtime. DMS can perform a full load of the 200 GB database and then continuously replicate changes until the cutover, which is essential for a critical application that cannot tolerate extended downtime.
Variation 2. A company is migrating a 500 GB Oracle database to Amazon RDS for Oracle. The migration must complete within a 4-hour downtime window. The network bandwidth is 1 Gbps. Which migration approach minimizes the migration time?
medium- A.Use AWS Schema Conversion Tool (SCT) to convert the schema, then use AWS DMS for data migration.
- B.Use Oracle Data Pump to export and import the database.
- ✓ C.Use AWS DMS to perform a full load of the database to RDS.
- D.Use AWS DataSync to copy the database files to Amazon S3, then restore to RDS.
Why C: AWS DMS performs a full load directly from the source Oracle database to the target RDS for Oracle instance over the network, leveraging the 1 Gbps bandwidth efficiently. For a 500 GB database, a full load at 1 Gbps (theoretical max ~450 Gbps per hour) can complete in under 2 hours, well within the 4-hour window, without requiring intermediate storage or schema conversion.
Variation 3. A company is migrating a 2 TB on-premises Oracle database to Amazon RDS for Oracle. The migration must have minimal downtime and support ongoing replication. Which AWS service should be used to accomplish this?
medium- A.AWS Schema Conversion Tool (AWS SCT)
- B.AWS DataSync
- C.AWS Glue
- ✓ D.AWS Database Migration Service (AWS DMS)
Why D: AWS DMS is the correct choice because it supports homogeneous migrations (Oracle to Oracle) with minimal downtime through ongoing replication using change data capture (CDC). It can handle a 2 TB database by using a large enough replication instance and enabling task logging for validation, ensuring data consistency during the migration.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DBS-C01 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 DBS-C01 exam.