Oracle to Amazon Aurora PostgreSQL Migration Using DMS with CDC
A database team is migrating an on-premises Oracle database to Amazon Aurora PostgreSQL. The team needs to ensure minimal downtime and data consistency. Which approach should be used?
Quick Answer
The correct approach is to use AWS Database Migration Service (DMS) with ongoing replication via change data capture (CDC). This method is essential for an Oracle to Aurora PostgreSQL migration with minimal downtime because DMS first performs a full load of the source database and then continuously captures and applies incremental changes from Oracle’s redo logs to the target Aurora PostgreSQL instance. At cutover, you simply stop new writes to Oracle, let CDC catch up, and redirect traffic—ensuring data consistency without a lengthy maintenance window. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding of heterogeneous migrations and the critical role of CDC for near-zero downtime. A common trap is choosing a snapshot-based approach or a simple one-time export/import, which would require significant downtime. Remember the memory tip: “CDC keeps the clock ticking” — it’s the only way to keep changes flowing live during migration.
⚠ Common exam trap
Watch out — candidates often confuse AWS DMS with simpler dump-and-restore tools (pg_dump/pg_restore) or assume that a foreign data wrapper can perform a migration, when in fact DMS is the only AWS managed service designed specifically for heterogeneous database migrations with minimal downtime via CDC.
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 using change data capture (CDC)
AWS DMS with ongoing replication using change data capture (CDC) is the correct approach because it enables a live migration with minimal downtime. DMS can perform a full load of the Oracle database and then continuously replicate ongoing changes from Oracle to Aurora PostgreSQL, ensuring data consistency at the point of cutover. This method avoids the need for a long maintenance window and supports heterogeneous migrations with automatic schema conversion.
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 the PostgreSQL foreign data wrapper (FDW) to link the Oracle database
Why it's wrong here
FDW is for querying, not for migration with minimal downtime.
- ✗
Use AWS Server Migration Service (SMS) to replicate the database
Why it's wrong here
SMS is for server migration, not databases.
- ✓
Use AWS Database Migration Service (DMS) with ongoing replication using change data capture (CDC)
Why this is correct
AWS DMS with ongoing CDC replication captures incremental changes from the Oracle source redo logs, enabling near-zero downtime migration by continuously synchronising transactions to Aurora PostgreSQL until cutover. This satisfies the stem’s requirement for minimal downtime and data consistency, as CDC maintains transactional integrity without halting the source database during the bulk load phase.
- ✗
Use pg_dump and pg_restore to migrate the data during a maintenance window
Why it's wrong here
This requires downtime and may not handle ongoing changes.
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Variation 1. A team is migrating an on-premises Oracle database to Amazon Aurora PostgreSQL. The database is 2 TB and has a 6-hour maintenance window. Which AWS service should the team use to minimize downtime?
medium- ✓ A.AWS Database Migration Service (AWS DMS)
- B.Amazon S3 Transfer Acceleration
- C.AWS Snowball Edge
- D.Amazon EC2 with Oracle installed
Why A: AWS DMS is the correct choice because it can perform a live migration from Oracle to Aurora PostgreSQL with minimal downtime using ongoing replication (change data capture). It supports heterogeneous migrations, automatically converting the source schema and data types, and can handle a 2 TB database within the 6-hour maintenance window by using multiple parallel tasks and large instance types.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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