Business Management System Database Migration Project from Oracle to PostgreSQL

We conducted a project to migrate the database infrastructure of a business management system from Oracle to PostgreSQL, aiming for cost optimization and system optimization.
This large-scale system comprises numerous business modules such as business planning, finance/accounting, operation management, and infrastructure monitoring, built using Java and .NET.
We formulated a migration plan to minimize risks associated with changing the database engine while leveraging existing application assets. As a result, we achieved a significant reduction in licensing costs and completed the migration to a stable new environment without compromising current business logic or performance.

Technology Stack & Development Tools

• Programming Languages: Java, .NET
• Database: Oracle, PostgreSQL
• Task Management Tool: Excel
• Communication Tool: Email/Zoom
• AI Tool: AI

Client Challenges

• Soaring Licensing Costs and Need for Operational Cost OptimizationThe Oracle database the client had been using for many years incurred high licensing fees, which was a major obstacle to their company-wide goal of reducing operational costs. To ensure stable future operations, there was an urgent need to migrate to PostgreSQL, a more cost-effective open-source database, while maintaining functionality and performance. However, since this system supports core business operations, compromising quality for cost reduction was not an option.
• Infrastructure Revamp with Minimal Impact on Existing SystemA prerequisite for changing the foundation of the system—the database—was to have absolutely no negative impact on existing performance, data integrity, or daily business operations. With numerous Java and .NET applications running, the requirement was to safely replace only the backend database without modifying, or with minimal modifications to, the application logic. This was an extremely challenging migration task.
• Ensuring Absolute Safety and VerifiabilityIn a migration project, data loss or system downtime is unacceptable. Therefore, transparency and safety throughout the migration process, as well as the verifiability of all conversion results, were strongly required. It was necessary to objectively prove not only that data was migrated but also that business logic functioned exactly as before, ensuring a smooth transition that would not interrupt user operations.

Client Requirements

• Complete Migration of DB Objects and Compatibility AssuranceThe client required that all DB objects running in the Oracle environment be migrated to the PostgreSQL environment without omission. It was necessary not just to copy data, but to accurately rewrite the logic of Oracle-specific functions and procedures to match PostgreSQL specifications, redefining the structure so that the same functions would operate in the new environment.
• Application Code Modification and Operation GuaranteeAlong with the database change, Java and .NET source code on the application side needed to be modified to prevent inconsistencies in SQL calls and DB connection processing. The requirement was to resolve compilation errors and absorb behavioral differences caused by different database drivers, ensuring the entire application could seamlessly integrate with PostgreSQL.
• Strict SQL Review and Integration TestingThe client requested a detailed review and correction of converted SQL statements to ensure they operated correctly according to PostgreSQL syntax rules and logic. Furthermore, we were required to conduct integration tests based on a detailed checklist provided by the client and prove with specific evidence that the system behaved exactly the same as before the migration.

Our Proposal & Approach

• Comprehensive System Analysis and Dependency IdentificationAt the start of the project, to grasp the full scope of the system, we conducted a thorough collection and analysis of all DB objects, executed SQL statements, and source code dependent on the database. This allowed us to visualize necessary migration points and potential risks at an early stage, accurately identify the scope of impact, and formulate a solid migration plan devoid of rework.
• Automation and Efficiency in Conversion Using Generative AITo prevent errors from manual conversion of huge amounts of DB objects and SQL, we introduced an automated conversion process using AI. Entrusting routine syntax conversions to AI significantly reduced manual effort while improving accuracy. Engineers were able to focus on adjusting complex business logic and handling exceptional cases, realizing high-quality migration in a short period.
• Rigorous Comparative Verification via Parallel Operation of Old and New EnvironmentsTo ensure migration reliability, we built two test environments: a copy of the current environment using Oracle and a new environment using PostgreSQL, and conducted parallel testing. By comparing the results of both environments in real-time using the same data and input conditions, we established a system to immediately detect minute behavioral differences or data inconsistencies and rapidly cycle through corrections.
• Thorough Evidence-Based Business Integration TestingBeyond unit testing for individual SQL statements, we conducted integration testing at the business scenario level based on the client’s checklist. Notably, we performed the same operations in both the old and new environments and collected and compared the results (evidence such as screenshots and logs). This guaranteed that for end-users utilizing the system, operability and results remained completely unchanged from before the migration.