It is hard to say which DBMS is better – Oracle or PostgreSQL, since both systems are high performance, very popular and have wide range of tools and APIs. However, the main disadvantage of Oracle is strict licensing terms and high total cost of ownership. On the other hand, PostgreSQL comes with less restrictive licenses and even better – it is open source. This is one of primary reasons why many database specialists consider migration from Oracle to PostgreSQL.

Database migration from Oracle to PostgreSQL is usually arranged according to well-known extract-transform-load (ETL) approach that includes these basic stages: 

• Schemas, indexes and constraints are extracted from Oracle database as SQL CREATE-statements
• These Oracle SQL statements are converted to comply with PostgreSQL syntax that includes safe types mapping, replacement of keywords, operators and built-in functions missing in the target DBMS
• Then the resulting DDL statements must be imported into PostgreSQL database
• Data of each Oracle table being converted is exported into comma separate values (CSV) files as an intermediate storage
• Transformation of binary data, dates and escaping special symbols in text fields according to PostgreSQL format must be applied to the data when it is required
• The processed data must be loaded from CSV files into the corresponding PostgreSQL tables
• Stored procedures, triggers and views are extracted from Oracle database as CREATE-statements and source code
• All of these statements and source code have to be converted to comply with PostgreSQL dialect of SQL and then loaded into the target database

The brief structure of migration procedure specified above indicates that Oracle to PostgreSQL database migration is quite hard and tedious procedure when doing it manually, especially for complex corporate scale data warehouses. Database specialists willing to automate Oracle to PostgreSQL migration and avoid risks of data loss or corruption caused by human factor often use special database migration software. 

There are multiple companies offer high quality database migration software. One of such migration tools has been developed by Intelligent Converters, a software vendor specializing in database migration and synchronization for years. Here is the list of their Oracle to PostgreSQL converter features:

1. All database objects such as table definitions, data, constraints, indexes, foreign keys and views are converted
2. All versions of Oracle and PostgreSQL are supported including “software as a service” (SAAS) variations of these database management systems 
3. High performance of the conversion due to efficient algorithms of reading and writing the data
4. Command line support for purpose of automating and scheduling Oracle to PostgreSQL migration
5. Options to merge and to synchronize existing PostgreSQL database with Oracle data
6. All conversion settings can be stored into profile to simplify next run of the migration for the same databases

To learn more about the product please visit the official site of Intelligent Converters.