Architecting Zero-Downtime Migrating Oracle Database from AWS RDS to Oracle ExaCS

Migrating mission-critical, Very Large Databases (VLDBs) across cloud ecosystems requires a balance of precision, performance, and risk mitigation. Moving an Oracle 19c workload from AWS RDS Standard Edition to Oracle Exadata Cloud Service (ExaCS) is a significant architectural shift that demands a robust Zero Downtime Migration (ZDM) strategy.

I recently architected a migration path from AWS RDS (Standard Edition) to Oracle Exadata Cloud Service (ExaCS) using OCI Goldengate to achieve a near-zero downtime transition. For any architect, the “Standard to Exadata” jump is a game-changer for performance and scalability.

Here is the high-level technical roadmap:

Architecture: Zero Downtime Migration — AWS RDS to Oracle ExaCS via OCI Goldengate

1. Environmental Hardening: Preparing the source RDS instance involves configuring supplemental logging and log retention while integrating Amazon S3 to act as the primary staging area for the initial data transfer.
   
   

2. Target Provisioning: Setting up the ExaCS environment with specific initialization parameters, tablespace structures, and establishing secure connectivity (DB Links and AWS CLI configuration) directly from the Exadata nodes.
   
   

3. The Hybrid Initial Load: Utilizing Oracle Data Pump to export full metadata and data to S3, followed by a high-speed transfer to ExaCS. Handling constraints and triggers at this stage is critical to ensure data integrity during the subsequent synchronization.
   
   

4. Continuous Data Capture (CDC): Deploying OCI Goldengate to bridge the gap. We initiate the Extract process on RDS and Replicat threads on ExaCS to synchronize all changes that occurred during the initial load, monitoring for sub-second lag.
   
   

5. Optimization & Validation: Before cutover, we perform dictionary and fixed-object stats gathering on ExaCS to ensure the optimizer is ready for the production workload, followed by rigorous object and constraint validation.
   
   

6. Orchestrated Cutover: With lag at zero, we perform a controlled application shutdown, finalize sequence synchronization, and redirect traffic to the ExaCS endpoint.

The result is a modernized database tier on the most powerful cloud infrastructure available for Oracle, with a minimal impact on the business.

If you’re planning a similar migration or want to explore what Exadata Cloud Service could mean for your estate, get in touch with DSP-Eclipsys to discuss your approach.