Everything About Oracle to PostgreSQL Migration

Many organizations now find the Oracle database a growing constraint. Licensing costs increase as systems scale. Simple changes need complex approvals. Infrastructure becomes tightly coupled to a specific vendor. This makes cloud adoption and architectural flexibility harder over time. As a result, teams spend more time maintaining the database system. Instead of delivering new features.

This is why Oracle to PostgreSQL migration has become a practical step. PostgreSQL is an open source database. It offers mature transaction handling and advanced features without vendor lock-in. It supports modern application architectures and scales well in cloud environments.

This guide explains how to migrate Oracle database to PostgreSQL in a structured way. We cover planning, schema conversion, data migration, tools, and common risks. This should help teams move safely and preserve data integrity.

Key Takeaways

• Oracle to PostgreSQL migration reduces licensing costs and increases flexibility.
• Careful schema assessment and data type mapping are critical.
• Data migration and testing must be planned as a single process.
• Change data capture enables near-zero downtime migration.
• Choosing the right migration tools reduces risk and effort.

Brief Overview of Oracle and PostgreSQL

Oracle is an enterprise database commonly used for high-volume transactions and complex applications. An Oracle database usually runs on a dedicated Oracle server. It relies on tightly integrated, proprietary tools.

PostgreSQL database is known for standards compliance, extensibility and strong concurrency control. PostgreSQL supports advanced indexing, JSON, and custom extensions. This makes it suitable for modern cloud and microservice architectures.

An Overview of PostgreSQL

PostgreSQL provides ACID compliance and flexible concurrency control. A PostgreSQL instance can be tuned for memory resources and large data volumes. This database also supports extensibility through extension modules and foreign data wrapper capabilities. This allows access to external source databases.

If you look at PostgreSQL next to Oracle, the architecture is different. But the practical results are often similar. In many production environments, PostgreSQL handles the same workloads with stable performance. Also, the open-source ecosystem makes a difference. Changes are visible, development moves fast, and no lock-in to a single vendor’s roadmap.

Why Should You Migrate from Oracle to PostgreSQL?

In most cases, the push to migrate starts with cost and control. Oracle licensing becomes more expensive as systems grow. Especially when the database size and CPU usage increase. Over time, this makes scaling predictable workloads costly and harder to plan for.

PostgreSQL offers:

• Lower total cost of ownership
• Flexible deployment options for cloud and on-premise
• Strong performance for OLTP workloads
• A large open source community and ecosystem

Many enterprises now run PostgreSQL in mission-critical production environments. For example, finance, healthcare and SaaS platforms.

Challenges in Oracle to PostgreSQL Migration

Migration from Oracle to PostgreSQL introduces several technical challenges:

• Differences in SQL dialects and PostgreSQL syntax
• PL/SQL vs PL/pgSQL differences in stored procedures
• Data type mismatches and null values handling
• Empty string behavior and the null operator
• Conversion of triggers, sequences and Oracle objects

Oracle treats empty string values as null. PostgreSQL distinguishes between empty string and null values. These differences must be addressed carefully during the conversion process.

Oracle to PostgreSQL Migration Process

Step 1: Planning and Assessment

Oracle to PostgreSQL conversion starts with a schema assessment of the source database. Teams review the Oracle schema, database size, dependencies, and table structures. This step identifies incompatible Oracle objects, SQL functions and Oracle code.

A migration strategy is defined depending on risk tolerance and system complexity.

Step 2: Database Schema Conversion

Database schema conversion transforms the Oracle schema into a PostgreSQL compatible schema. Schema conversion includes tables, foreign key constraints, indexes, sequences and views.

Tools analyze the Oracle database schema and generate SQL scripts for PostgreSQL. Schema conversion must also address differences in data type definitions and default values.

Step 3: Data Migration

Data migration moves source data from the Oracle database to target databases running on PostgreSQL. The data migration process usually includes:

• Export data from the Oracle source
• Initial load into the PostgreSQL instance
• Validation of row counts and data integrity

For large data volumes, transferring data in parallel reduces migration time. Data integrity checks ensure that Oracle data matches the PostgreSQL target after migration.

Step 4: Change Data Capture and Synchronization

For systems requiring minimal downtime, change data capture is essential. Change data capture reads transaction logs or uses supplemental logging on the Oracle server. It is necessary to capture ongoing changes.

Captured changes are applied to the PostgreSQL instance as they happen. This keeps both systems in sync. This also makes it possible to switch over with no downtime and avoid interruptions to operations.

Step 5: Application Migration and Testing

You should update applications to support PostgreSQL syntax and SQL scripts. Stored procedures and triggers are rewritten in PL/pgSQL and tested.

Testing includes functional testing, performance testing and validation of write operations under load. Network connectivity and the server’s timezone settings are also verified.

Step 6: Go-Live and Post-Migration Activities

The final step switches production workloads to the PostgreSQL server. A final data capture cycle ensures no data loss. Monitoring confirms stability, and performance tuning optimizes memory resources and concurrency control.

Migration Tools for Oracle to PostgreSQL

Several migration tools support Oracle to PostgreSQL migration:

• ora2pg – Open source tool that converts Oracle objects and generates SQL scripts
• AWS Schema Conversion Tool – Automates schema conversion and assessment
• pgLoader – Efficient for direct data migration and initial load

Oracle to PostgreSQL migration tools vary in automation level. Most tools assist with schema conversion and exporting data. But they still require manual validation and testing.

Data Types, Null Values and Compatibility

Data type mapping is a critical part of database migration. Oracle and PostgreSQL differ in numeric precision, date handling and character types.

Special attention is required for:

• Null values and empty string handling
• Primary key and foreign key definitions
• Default values and constraints

PostgreSQL syntax differs from Oracle SQL, and careful testing ensures correctness.

Conclusion

Converting from Oracle to PostgreSQL is often part of an effort to modernize the database layer. Teams usually do it to lower licensing costs and get more flexibility in how systems are built. To succeed, plan the migration carefully, with schema conversion and testing at every stage.

You should understand the migration process and select the right tools. This helps teams safely move from Oracle to PostgreSQL and build a scalable foundation for future growth.

If you don’t have the capacity to manage every step internally, specialized migration services can help ensure a stable transition and long-term reliability.