AWS Database Migration Service
Database migration and replication
DMS migrates data between databases (same or different types) with low downtime: it copies all the data, then continuously replicates changes (CDC); Schema Conversion is included to convert schemas when engines differ.
- Cost$$ Medium
- Difficulty●●●●●
- Costs money when idle?Yes
- Managed by AWS
- In examsCLF · SAA · SOA
Think of it asLike moving house while still living there: things are moved gradually, and anything new you buy is also sent to the new house until moving day.
When to use it
✓ Use it when
Moving a database to AWS or changing engines (Oracle → Aurora PostgreSQL), or continuously replicating into a data lake.
✗ Avoid it when
Moving only files/objects → DataSync; moving entire servers → Application Migration Service.
Common uses
- Moving on-prem Oracle/SQL Server to RDS/Aurora
- Changing engines with Schema Conversion
- CDC streaming changes into S3/Redshift
What does it cost?
- Pricing model: Charged per hour for the replication instance and its storage, or per capacity unit with DMS Serverless; data transfer is charged separately.
⚠️ Cost traps
Forgetting to delete the replication instance after the migration is done.
Related services
SAA-C03 study guide
DMS is covered in these study modules: