The Database Migration Service of AWS

DMS AWS (Database Migration Service of Amazon Web Service) is a cloud-based service that enables migration of data warehouses, relational databases, and NoSQL databases. Data migration with DMS AWS is either from on-premises databases to the cloud or from one cloud provider to another. An advantage of this process is that the source databases remain fully functional always and hence downtime is not required.

The Functioning of DMS AWS

For migration with this cloud-based replication software, a link has to be first created between the source and target data bases to inform DMS AWS which is the source database and the intended location. This is followed by defining a task to move the data from the source to the target.

It is a completely automated process and does not require human intervention even if the tables and the keys needed for migration are absent in the target database. In such cases, the AWS SCT (AWS Schema Conversion Tool) is used for creating indexes, tables, triggers, and views at the target database.

By migrating databases with the DMS AWS, organizations get all the benefits of the cloud environment such as enhanced performance, security, data usage flexibility, and cost efficiencies.

Types of Database Migration with DMS AWS

Two types of database migration are possible with DMS AWS.

Homogeneous Database Migration

This form of migration is undertaken when the database engines, data codes, data types, and schema structures of the source and the target databases are the same. Migration here is a one-shot activity where whole databases are moved at a time once the source and the target are linked. Examples of homogeneous migration include Microsoft SQL Server to Amazon RDS for SQL Server, and MySQL to Amazon RDS for MySQL. MySQL to Amazon Aurora, and Oracle to Amazon RDS for Oracle.

Heterogeneous Database Migration

Here, for migration, the source and the target databases should have different database engines, data codes, data types, and schema structures. Data migration in this method is a two-step activity. First, the data code, data type, and schema structure of the source database are converted to match that of the target database with the help of the AWS SCT tool. The next step is the migration proper. The most common forms of heterogeneous migration are Oracle to PostgreSQL, Microsoft SQL Server to MySQL migrations, and Oracle to Amazon Aurora.

Organizations have to choose one depending on the structure of their databases.

Even though database migration with DMS AWS is a seamless and automated activity, there are certain limitations too. These arise when converting data types, codes, and schema structures of the source to match that of the target. It is because the conversions are not handled directly by DMS AWS but through the AWS SCT tool. Further, to migrate incremental data after full load migration (Change Data Capture), a good amount of additional coding is required.