There are some external tools to help migrate Oracle database to PostgreSQL, paid or free. Here, 4 external tool that can you try.
Software is able to convert 1 Million of records in 4-5 minutes.
Trigger-based database sync method and simultaneous Bi-directional
synchronization help you to manage your data easy and efficiently.
A toolkit migrates Oracle databae to PostgreSQL in wizard. It connects
to Oracle and PostgreSQL database directly, and migrate its table
structure, data, indexes, primary keys, foreign keys, comments and so on.
Ora2Pg is a Perl module to export an Oracle database schema to a
PostgreSQL compatible schema. It connects your Oracle database, extracts
its structure, and generates an SQL script that you can load into your
PostgreSQL database.
Database conversion between Oracle (and 30+ other database engines) and
PostgreSQL. With everything on localhost, typical throughput over 100k
records per second.
