AWS Database Migration Service

What it is

AWS Database Migration Service (AWS DMS) migrates relational databases, data warehousesData warehouseA database designed for analytics, holding cleaned, structured data from many sources, so that reports and queries across years of history run fast. Amazon Redshift is the AWS data warehouse.Glossary entryClose, NoSQLNoSQLDatabases that store data in models other than relational tables, such as key-value, document, wide-column, or graph, usually to scale out easily or to handle data whose shape varies. Amazon DynamoDB is a NoSQL database.Glossary entryClose databases, and other data stores into AWS, or between cloud and on-premisesOn-premisesIn data centers or offices that you run yourself, rather than in the cloud. Hybrid architectures connect on-premises systems to AWS, for example through AWS Direct Connect or a VPN.Glossary entryClose systems. It can do a one-time migration or replicate ongoing changes to keep the source and target in sync, so the source database stays available to applications during the migration and cutover takes very little downtime.

Choose DMS when a question asks to migrate a database to AWS with minimal downtime, to move between database engines (for example Oracle to Aurora PostgreSQL), or to continuously replicate data from one database to another, such as into S3 or Redshift for analytics.

Concepts

• Source and target endpoints: connection details for the databases. Supported sources and targets include Oracle, SQLSQL (Structured Query Language)The standard language for querying and changing data in relational databases. Analytics services such as Amazon Athena and Amazon Redshift also use SQL.Glossary entryClose Server, MySQL, MariaDB, PostgreSQL, MongoDB, and SAP, and AWS services such as Aurora, RDS, Redshift, DynamoDB, S3, OpenSearch Service, and Kinesis.
• Replication instance: the managed EC2-based server that runs the migration. Choose Multi-AZMulti-AZRunning standby or extra copies of a resource in other Availability Zones so that it survives the loss of one. An Amazon RDS Multi-AZ deployment keeps one or two standby copies and fails over to one automatically.Glossary entryClose for a synchronous standby replica in another Availability ZoneAZ (Availability Zone)An isolated location within an AWS Region, made up of one or more data centers with their own power, cooling, and networking. The AZs in a Region are linked by fast, low-latency connections, so spreading resources across them protects against the failure of one site.Glossary entryClose and automatic failoverFailoverSwitching automatically to a standby resource when the primary one fails, such as a standby database in Amazon RDS or a backup site chosen by Route 53 failover routing.Glossary entryClose.
• DMS Serverless: automatic provisioning, scaling, built-in high availabilityHA (High availability)The ability of a system to keep serving users when parts of it fail, usually by running redundant copies across Availability Zones and failing over automatically. It is often stated as a percentage of uptime, such as 99.99%.Glossary entryClose, and pay-for-use billing, with no replication instance to size or patch.
• Migration task types:
  • Full load: copy the existing data.
  • Full load and CDCCDC (Change data capture)Capturing each insert, update, and delete in a source database as it happens, so that another system can be kept in step. AWS DMS uses CDC to keep replicating changes after the initial full load.Glossary entryClose ("migrate existing data and replicate ongoing changes"): copy, then keep applying changes until you cut over.
  • CDC only ("replicate data changes only"): apply changes from a point in time, for example after a native bulk load.
• Basic schema only: when DMS creates the target tables, it creates only tables and primary keys. It does not create secondary indexes, foreign keys, or user accounts; create them with native tools or schema conversion. Add secondary indexes before the CDC phase so that changes don't cause full table scans, and enable triggers at cutover.
• Homogeneous data migrations: same engine on both sides, such as PostgreSQL to RDS for PostgreSQL or Aurora PostgreSQL. DMS uses native database tools and runs them serverless.
• Heterogeneous migrations: different engines. First convert the schema, then migrate the data:
  • DMS Schema Conversion converts source schemas and code objects (views, stored procedures, functions) to a format for Aurora, RDS, or Redshift. It is a managed feature in the DMS console, with nothing to install.
  • The downloadable AWS Schema Conversion Tool (AWS SCT) does the same conversion as a desktop application that you install on your computer.
• Data validation: compare source and target rows to confirm the data migrated correctly.
• DMS Fleet Advisor, which discovered on-premises databases for migration planning, reached end of support on May 20, 2026. Don't choose it in a new design.

Security, resilience, performance, and cost

Security

• Run replication instances in a VPC. Encrypt storage with KMS (a customer managed keyCustomer managed keyA KMS key that you create, own, and manage: you control its key policy, rotation, and deletion. AWS managed keys, in contrast, are created and managed for you by an AWS service.Glossary entryClose if required) and connections with TLSTLS (Transport Layer Security)The protocol that encrypts traffic between a client and a server and lets the server prove its identity with a certificate. It replaced SSL, though the older name is still common; HTTPS is HTTP over TLS.Glossary entryClose. Endpoints can read database credentials from Secrets Manager, which can rotate them, so passwords aren't stored in the endpoint settings.
• To keep replication off the public internet, make the replication instance not publicly accessible and reach on-premises databases over Direct Connect or VPNVPN (Virtual private network)An encrypted tunnel over a public network, such as the internet, that joins networks or devices as if they were directly connected. AWS Site-to-Site VPN connects networks; AWS Client VPN connects individual users.Glossary entryClose.

Resilience

• Use Multi-AZ replication instances (or DMS Serverless) for high availability during long migrations; CDC keeps the target current until cutover. Multi-AZ protects ongoing replication (CDC); a full load task interrupted by a failover fails, and you restart it for the unfinished tables.

Performance

• Size the replication instance (or let Serverless scale), and run several tasks in parallel for large databases. For very large initial loads, combine native tools with CDC-only tasks.

Cost

• Pay for replication instance hours and storage, or DMS Serverless capacity, plus data transfer.
• Database Savings Plans cover DMS.

Monitoring

• CloudWatch metrics for tasks and instances, such as CDC latencyLatencyThe time between sending a request and receiving the response, usually measured in milliseconds. Distance and processing add to it; caching and serving users from nearby locations reduce it.Glossary entryClose; task logs in CloudWatch Logs; table statistics and validation results.

DMS or another option?

If the requirement is	Choose
Migrate a database with minimal downtime	AWS DMS with full load and CDC
Change engines, such as Oracle to Aurora PostgreSQL	DMS Schema Conversion or AWS SCT, then DMS
Convert the schema with no software to install	DMS Schema Conversion
Continuously replicate database changes into S3 or Redshift	AWS DMS CDC
Move whole servers, including databases installed on them	AWS Application Migration Service
Copy files and file shares	AWS DataSync

Reverse mindmap: when the question points here

• Yes, when the question says
  • Migrate a database to AWS with minimal downtime→ leads to DMS
  • Source database must stay online during migration→ leads to DMS full load and CDC
  • Replicate ongoing changes to another database→ leads to DMS CDC
  • Stream database changes to S3, Kinesis, or Redshift→ leads to DMS
• Different engines
  • Convert schema and code first→ leads to DMS Schema Conversion or AWS SCT
  • No software may be installed→ leads to DMS Schema Conversion
• Run it well
  • No replication instance to size→ leads to DMS Serverless
  • High availability during migration→ leads to Multi-AZ replication instance
  • Confirm rows match→ leads to Data validation
  • Target missing indexes after migration→ leads to Create secondary indexes yourself, before CDC
  • No passwords in endpoints, no internet path→ leads to Secrets Manager, private replication instance
• No, when the question says
  • Move the whole server→ leads to Application Migration Service
  • Copy files→ leads to DataSync

Key takeaways

• AWS DMS migrates databases with the source still running, using full load, full load plus CDC, or CDC only.
• Heterogeneous migrations need schema conversion first, with DMS Schema Conversion (managed) or AWS SCT (desktop).
• DMS creates only tables and primary keys; create secondary indexes, foreign keys, and users yourself.
• Replication instances can be Multi-AZ; DMS Serverless removes instance management.
• Targets include Aurora, RDS, Redshift, DynamoDB, S3, OpenSearch Service, and Kinesis.

Sources

• AWS DMS User Guide: What is AWS Database Migration Service?
• AWS DMS User Guide: Sources for data migration
• AWS DMS User Guide: Targets for data migration
• AWS DMS User Guide: Working with an AWS DMS replication instance
• AWS DMS User Guide: Working with AWS DMS Serverless
• AWS DMS User Guide: Creating a task
• AWS DMS User Guide: Creating tasks for ongoing replication
• AWS DMS User Guide: Homogeneous data migrations
• AWS DMS User Guide: Migrating databases to their Amazon RDS equivalents
• AWS DMS User Guide: Using secrets to access endpoints
• AWS DMS User Guide: Converting database schemas using DMS Schema Conversion
• AWS DMS User Guide: AWS DMS data validation
• AWS DMS User Guide: Best practices
• AWS Schema Conversion Tool User Guide: What is the AWS Schema Conversion Tool?
• AWS DMS pricing