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Minimizing Downtime for Oracle to RDS Migration Using AWS DMS

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. The database is 500 GB in size and has a 24/7 uptime requirement. The migration window is limited to 2 hours. Which strategy should be used to minimize downtime?

Quick Answer

The answer is to use AWS Database Migration Service (DMS) with ongoing replication because it directly addresses the need to minimize downtime when migrating Oracle to RDS Oracle. AWS DMS performs a full load of the 500 GB database while continuously capturing and applying change data capture (CDC) from the source, allowing the source to remain fully operational until the final cutover window. This technique keeps the replication lag minimal, so the actual switchover can be completed within the two-hour limit by simply stopping new transactions and applying the last few seconds of changes. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding of how to balance data volume against strict uptime requirements; a common trap is choosing a full native export/import or a snapshot restore, both of which would exceed the allowed downtime for a database of this size. Remember the key principle: for large, always-on databases, DMS with ongoing replication is the only method that decouples the lengthy data transfer from the short cutover window. A useful memory tip is "DMS keeps the clock ticking—full load runs while CDC catches the ticks."

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 Database Migration Service (DMS) with ongoing replication

AWS Database Migration Service (DMS) can perform ongoing replication from the source Oracle database to Amazon RDS for Oracle, allowing a minimal cutover window of under 2 hours. Option A is incorrect because AWS Schema Conversion Tool (SCT) only converts schema and does not handle data migration. Option B is incorrect because performing an on-premises backup and restoring via Oracle RMAN would require significant downtime and may exceed the 2-hour window for a 500 GB database. Option C is incorrect because exporting to a dump file and importing into RDS requires the database to be offline or in read-only mode, causing prolonged 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 Schema Conversion Tool (SCT) to convert the schema and copy data

    Why it's wrong here

    SCT converts schema but does not migrate data continuously.

  • ✗

    Take an on-premises backup and restore to RDS using Oracle RMAN

    Why it's wrong here

    Restoring 500 GB via RMAN may exceed the 2-hour window.

  • ✗

    Export the database to a dump file and import into RDS

    Why it's wrong here

    Export/import is slow and requires application downtime.

  • ✓

    Use AWS Database Migration Service (DMS) with ongoing replication

    Why this is correct

    DMS supports minimal downtime by replicating changes until cutover.

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Same concept, more angles

1 more way 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 is migrating an on-premises Oracle database to Amazon RDS for Oracle. During the migration, they need to ensure minimal downtime. Which AWS service should be used for the migration?

easy
  • ✓ A.AWS Database Migration Service
  • B.AWS DataSync
  • C.Amazon S3 Transfer Acceleration
  • D.AWS Server Migration Service

Why A: AWS Database Migration Service (DMS) is the correct choice because it is specifically designed for migrating databases to AWS with minimal downtime. DMS supports homogeneous migrations (e.g., Oracle to Oracle) and heterogeneous migrations (e.g., Oracle to Amazon Aurora), and it can perform continuous replication using change data capture (CDC) to keep the source and target databases synchronized during the migration, allowing you to cut over with only a brief pause.

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.