AWS Database Migration Service (DMS) Overview

AWS Database Migration Service (DMS) helps you migrate databases to AWS easily and securely. The source database remains fully operational during the migration, minimizing downtime to applications. DMS can migrate your data to and from most widely used commercial and open-source databases.

Database Migration Service (DMS) support following use case types:

  1. Homogenous migrations such as Oracle to Oracle

  2. Heterogeneous migrations such as Oracle to Amazon Aurora or Microsoft SQL Server to MySQL.

  3. Streaming data to Redshift, DynamoDB, and S3 from any of the supported sources including Amazon Aurora, PostgreSQL, MySQL, MariaDB, Oracle, SAP ASE, SQL Server and MongoDB, enabling consolidation and easy analysis of data in the petabyte-scale data warehouse.

  4. Continuous data replication with high-availability.

After migration has started, DMS takes care of all complexities like data type transformation, compression and parallel transfer, along with replicating changes to source database during the migration.


AWS Schema Conversion Tool (SCT)

The AWS Schema Conversion Tool makes heterogeneous database migrations easy by automatically converting the source database schema and a majority of the custom code, including views, stored procedures, and functions, to a format compatible with the target database. Any code that cannot be automatically converted is clearly marked so that it can be manually converted.

SCT can also scan your application source code for embedded SQL statements and convert them as part of a database schema conversion project. During this process, SCT performs cloud native code optimization by converting legacy Oracle and SQL Server functions to their equivalent AWS service thus helping you modernize the applications at the same time of database migration.

Once schema conversion is complete, SCT can help migrate data from a range of data warehouses to Amazon Redshift using built-in data migration agents. Your source database can be on-premises, or in Amazon RDS or EC2 and the target database can be in either Amazon RDS or EC2. Supported conversions by SCT is available at dms page.

SCT provides integration with DMS  and allows you to create DMS endpoints and tasks. SCT also allows you to run and monitor the DMS tasks from SCT.


DMS Use Cases Summary (based on Amazon docs)

Homogeneous Database Migrations

Here, the source and target database engines are the same or are compatible like Oracle to RDS for Oracle, MySQL to Amazon Aurora, MySQL to RDS for MySQL etc.

This kind of migration is a one step process. You create a migration task with connections to the source and target databases, then start the migration with the click of a button

The source database can be located in your own premises, running on an EC2 instance, or it can be an RDS database. The target can be a database in EC2 or RDS.


Heterogenous Database Migrations

In heterogeneous database migrations the source and target databases engines are different, like in the case of Oracle to Amazon Aurora, Oracle to PostgreSQL migrations.

Here, the schema structure, data types, and database code of source and target databases can be quite different, requiring a schema and code transformation before the data migration starts.

Heterogeneous migrations is a two step process. First use the SCT to convert the source schema and code to match that of the target database, and then use DMS to migrate data from the source database to the target database. DMS will take care of all data type conversions automatically.

The source database can be located in your own premises, running on an EC2 instance, or it can be an RDS database. The target can be a database in EC2 or RDS.


DMS can also be used to:

  • Migrate data both into and out of the cloud for development purposes.

  • Consolidate multiple source databases into a single target database.

  • Continuous data replication. 

References (Deprecated): 

Learn Serverless from Serverless Programming Cookbook


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About is my blog to share notes and learning materials on Cloud and Data Analytics. My current focus is on Amazon Web Services.

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