In certain customer scenarios, Amazon RDS for Oracle databases need to connect to external data sources, such as RDS for PostgreSQL. PostgreSQL can establish connections to Oracle databases using a foreign data wrapper (FDW). In this post, we walk you through setting up an EC2 instance as a database gateway server. You will install and configure Oracle Database Gateway for ODBC (DG4ODBC), ODBC drivers, a PostgreSQL client, and PostgreSQL libraries. With this setup, you can create database links on RDS for Oracle to connect to PostgreSQL through this gateway.