Prerequisites

Understand Amazon Relational Database Service (Amazon RDS), the applicable database technologies, and SQL.

Create a user with Amazon Identity and Access Management (IAM) credentials that allows you to launch Amazon RDS and Amazon Database Migration Service (Amazon DMS) instances in your Amazon Web Services Region. For information about IAM credentials, see Setting up for Amazon RDS.

Understand the Amazon Virtual Private Cloud (Amazon VPC) service and security groups. For information about using Amazon VPC with Amazon RDS, see Amazon Virtual Private Cloud (VPCs) and Amazon RDS. For information about Amazon RDS security groups, see Amazon RDS Security Groups.

Understand the supported features and limitations of Amazon DMS. For information about Amazon DMS, see https://docs.aws.amazon.com/dms/latest/userguide/Welcome.html.

Understand the supported data type conversion options for Oracle and PostgreSQL. For information about data types for Oracle as a source, see Using an Oracle database as a source. For information about data types for PostgreSQL as a target, see Using a PostgreSQL Database as a Target.

Size your target PostgreSQL database host. DBAs should be aware of the load profile of the current source Oracle database host. Consider CPU, memory, and IOPS. With RDS, you can size up the target database host, or reduce it, after the migration. If this is the first time you are migrating to PostgreSQL, then we recommend that you have extra capacity to account for performance issues and tuning opportunities.

Audit your source Oracle database. For each schema and all the objects under each schema, determine if any of the objects are no longer being used. Deprecate these objects on the source Oracle database, because there’s no need to migrate them if they are not being used.

If load capacity permits, then get the max size (kb) for each LOB type on the source database, and keep this information for later.

If possible, move columns with BLOB, CLOB, NCLOB, LONG, LONG RAW, and XMLTYPE to Amazon S3, Dynamo DB, or another data store. Doing so simplifies your source Oracle database for an easier migration. It will also lower the capacity requirements for the target PostgreSQL database.