AWS DMS (Amazon Web Service Database Migration Service) is a cloud-based service that enables quick and seamless migration of databases from on-premises servers to the cloud or from one cloud provider to another. At least one among the source or the target databases or both should be in the cloud for AWS DMS to function.

AWS database migration service allows either one-time migration or continual replication of data provided both the source and target databases are in sync. Hence, the source database remains fully functional during migration, and organizations do not have to shut down their systems. This is very convenient for large enterprises for whom downtime for any length of time can be very inconvenient.

A critical advantage of AWS database migration service is that databases can be migrated from the most common open-sourced ones and data can be consistently replicated with high availability. Several databases can also be combined into one petabyte-sized one through streaming of data to Amazon Redshift or Amazon S3. When databases are migrated to Amazon Redshift, Amazon DynamoDB, or Amazon Aurora, users get to use the AWS database migration service for free for the first six months.

Forms of migration with the AWS database migration service

AWS database migration service permits two forms of migration.

# Homogeneous database migration

This form of migration is done when the engines of the source and the target databases match each other. Examples of homogeneous migration are Microsoft SQL Server to Amazon RDS for SQL Server, MySQL to Amazon Aurora, Oracle to Amazon RDS for Oracle, or MySQL to Amazon RDS for MySQL. Since the engines are compatible and the data types, data codes, and schema structures are similar, the database migration process is simple and can be completed in one step.

AWS database migration service starts the process with a click on the Management Console as soon as a link between the source and the target database is established. This is regardless of whether the source database is an Amazon RDS or based outside the AWS and operating on an Amazon EC2 instance. The target database may be placed in the Amazon EC2 or the Amazon RDS.

# Heterogeneous Migration

As distinct from homogeneous migration, the movement of data is between the source and target databases that have different engines. Examples of heterogeneous migration include Oracle to Amazon Aurora, Microsoft SQL Server to MySQL migrations, or Oracle to PostgreSQL. The schema structures, data types, and data codes too are different and hence, before migration, a schema and code transformation have to be done.

This is a two-step process. In the first, the AWS Schema Conversion Tool converts the source database schema structure and code automatically to match that of the target database. Only then is the data migration started.

These are the reasons why you should use the database migration service of AWS.