Migrating to Amazon Aurora PostgreSQL: AWS DMS, SCT, and Best Practices
A company is migrating a large Oracle database to Amazon Aurora PostgreSQL. The migration must have minimal downtime and preserve data consistency. Which THREE AWS services or features should be used?
Quick Answer
The answer is AWS Database Migration Service (DMS) for continuous replication, AWS Schema Conversion Tool (SCT) for schema conversion, and a source Oracle database configured for ongoing change capture. This combination is correct because a heterogeneous migration from Oracle to Amazon Aurora PostgreSQL requires SCT to translate incompatible SQL dialects, stored procedures, and data types, while DMS handles the live data transfer with minimal downtime by continuously replicating changes from the source. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding that SCT is mandatory for schema conversion in any cross-engine migration, and that DMS’s ongoing replication feature is the key to achieving near-zero downtime. A common trap is assuming DMS alone can handle schema conversion—it cannot, as DMS only moves data, not the database objects. Remember the memory tip: “SCT for the structure, DMS for the data, and CDC for the cutover.”
⚠ Common exam trap
Watch out — candidates often confuse AWS DataSync (a file-transfer service) with database migration tools, or mistakenly think RDS for Oracle can serve as a migration target when the question explicitly specifies Aurora PostgreSQL.
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 Schema Conversion Tool (SCT) for schema conversion
Option C (AWS Schema Conversion Tool) is correct because migrating from Oracle to Aurora PostgreSQL requires converting the Oracle schema, stored procedures, and PL/SQL objects into PostgreSQL-compatible DDL, which SCT automates. Option D (Amazon Aurora PostgreSQL as the target database) is correct because the scenario explicitly states the migration target is Aurora PostgreSQL, so the target engine must be Aurora PostgreSQL. Option E (AWS DMS for continuous replication) is correct because DMS supports ongoing change data capture (CDC) from Oracle to Aurora PostgreSQL, enabling minimal downtime by replicating changes until cutover. Option A is incorrect because RDS for Oracle is the source engine, not the target, and would not accomplish the migration to PostgreSQL. Option B is incorrect because AWS DataSync is a file/object transfer service for data like NFS/SMB/S3, not a database migration tool, and cannot preserve relational data consistency for an Oracle-to-PostgreSQL migration.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Amazon RDS for Oracle as the target
Why it's wrong here
RDS for Oracle keeps the workload on Oracle, contradicting the stated target of Aurora PostgreSQL. It is tempting because RDS for Oracle is a valid managed destination when the goal is consolidating Oracle databases in AWS without engine change, but here the engine must actually change to PostgreSQL.
- ✗
AWS DataSync for initial load
Why it's wrong here
DataSync copies files and objects between storage systems; it cannot read Oracle table data or apply schema conversions. It is tempting because DataSync handles large bulk transfers well, and it would be correct when migrating file shares or S3 data rather than performing a database engine migration.
- ✓
AWS Schema Conversion Tool (SCT) for schema conversion
Why this is correct
AWS Schema Conversion Tool converts Oracle PL/SQL, sequences and data types into Aurora PostgreSQL-compatible DDL, satisfying the heterogeneous-engine schema transformation the migration demands. Without it, stored procedures and proprietary constructs would fail on PostgreSQL, blocking the minimal-downtime cutover that AWS DMS alone cannot address.
- ✓
Amazon Aurora PostgreSQL as the target database
Why this is correct
Aurora PostgreSQL supplies the managed target engine that DMS replicates into, supporting logical replication slots so changes stream continuously. This satisfies the minimal-downtime constraint, since cutover happens only after the target has fully caught up and consistency is verified.
- ✓
AWS Database Migration Service (DMS) for continuous replication
Why this is correct
DMS continuous replication (change data capture) streams ongoing Oracle changes to the target after the initial full load, keeping both databases synchronised. This directly satisfies the minimal-downtime constraint, because cutover occurs only once replication lag reaches zero.
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 DEA-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 its on-premises Oracle database to Amazon Aurora PostgreSQL. The migration must have minimal downtime. The source database is 2 TB and runs on a single server. Which AWS service should be used for the migration?
medium- A.AWS DataSync
- B.Amazon S3 Transfer Acceleration
- ✓ C.AWS Database Migration Service (DMS)
- D.AWS Snowball Edge
Why C: AWS Database Migration Service (DMS) is the correct choice because it supports homogeneous migrations from Oracle to Amazon Aurora PostgreSQL with minimal downtime using ongoing replication (change data capture). DMS can handle a 2 TB source database by performing a full load followed by continuous replication of changes from the Oracle redo logs, allowing the target Aurora database to stay nearly in sync until cutover.
Variation 2. A company is migrating an on-premises PostgreSQL database to Amazon Aurora PostgreSQL. The database is 2 TB in size. The migration must have minimal downtime. Which approach should the data engineer use?
hard- A.Use AWS Schema Conversion Tool (SCT) to convert the schema and then copy data using S3.
- B.Create an Aurora read replica from the on-premises database using native replication.
- ✓ C.Use AWS Database Migration Service (DMS) with ongoing replication to minimize downtime.
- D.Use pg_dump to export the database and pg_restore to import into Aurora.
Why C: AWS DMS with ongoing replication (change data capture) is the correct approach because it allows a full load of the 2 TB database followed by continuous replication of changes from the on-premises PostgreSQL source to the Aurora PostgreSQL target, minimizing downtime to a short cutover window. This is the only option that supports near-zero downtime migration for large databases by capturing ongoing transactions.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DEA-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 DEA-C01 exam.