Migrating and Modernizing Oracle Databases to PostgreSQL on AWS – Part 1: Discovery

This article explores the discovery phase of migrating Oracle databases to PostgreSQL on AWS, the foundational step determining migration success and the first part of a four-part series.

• Business drivers include cost optimization (Oracle's per-CPU licensing), competitive agility, and vendor independence through cloud-native PostgreSQL
• Technical drivers span architectural modernization (replacing Oracle AQ with SNS/SQS), performance scaling (Aurora read replicas vs. RAC), and broader talent availability
• Key Oracle-to-PostgreSQL differences: multi-process vs. multi-threaded architecture, tuple-based vs. undo-based MVCC, PL/SQL to PL/pgSQL conversion, and data type mapping (DATE, NUMBER, CLOB)
• Security model shifts from VPD/FGA to RLS/pgAudit, with IAM database authentication replacing long-lived passwords
• Discovery phase produces asset inventory, dependency graphs, requirements documents, and workload baselines to prevent implementation surprises
• ZCINS case study revealed 37 critical undocumented dependencies, demonstrating why comprehensive discovery prevents costly delays and post-cutover incidents

Thorough discovery transforms chaotic asset lists into structured roadmaps, reducing scope, protecting integrations, and enabling accurate impact analysis for successful Oracle-to-PostgreSQL modernization.