Before applying patches, it’s important to understand the difference between PSU and RU: - PSU (Patch Set Update): These are quarterly patches that include security and critical bug fixes. PSUs are conservative and less invasive, making them suitable for stable production systems. PSU (Patch Set Update): These are quarterly patches that include security and critical bug fixes. PSUs are conservative and less invasive, making them suitable for stable production systems. - RU (Release Update): RUs are more comprehensive, containing all PSU fixes plus additional improvements, new features, and optimizer changes. These are ideal for environments where continuous feature updates are acceptable. RU (Release Update): RUs are more comprehensive, containing all PSU fixes plus additional improvements, new features, and optimizer changes. These are ideal for environments where continuous feature updates are acceptable. Both are cumulative — meaning newer versions include previous fixes — but RUs are the preferred standard starting from Oracle 12.2 and later .

Applying patches safely begins with thorough preparation : - Identify the Current Version: or Identify the Current Version: or - Download the Correct Patch: Get the latest PSU or RU patch from My Oracle Support (MOS) . Always verify platform and database version compatibility. Download the Correct Patch: Get the latest PSU or RU patch from My Oracle Support (MOS) . Always verify platform and database version compatibility. - Check OPatch Utility Version: Ensure your OPatch tool is up to date: Check OPatch Utility Version: Ensure your OPatch tool is up to date: - Take a Full Backup: Use RMAN to take a full database backup or a snapshot if the environment is virtualized. Take a Full Backup: Use RMAN to take a full database backup or a snapshot if the environment is virtualized. - Check for Conflicts: Run a conflict check before patching: Check for Conflicts: Run a conflict check before patching: - Stop Database and Listeners (If Required): For database patches, ensure you stop all Oracle services cleanly: Stop Database and Listeners (If Required): For database patches, ensure you stop all Oracle services cleanly:

Once pre-checks are complete, proceed with the patching: - Unzip the Patch: Unzip the Patch: - Apply the Patch using OPatch: Apply the Patch using OPatch: - For RAC or Grid Infrastructure: Use to simplify patching across nodes: For RAC or Grid Infrastructure: Use to simplify patching across nodes: - Monitor the Log File: Check the patch logs under to confirm successful patching. Monitor the Log File: Check the patch logs under to confirm successful patching.

After patching, always perform the following validation steps: - Startup Database and Services: Startup Database and Services: - Execute Post-Installation SQL Scripts (if applicable): Some patches require SQL scripts to be run as SYSDBA: Execute Post-Installation SQL Scripts (if applicable): Some patches require SQL scripts to be run as SYSDBA: - Verify Patch Application: Verify Patch Application: - Check Database Functionality: Test basic operations, connectivity, and application performance. Check Database Functionality: Test basic operations, connectivity, and application performance. - Gather Updated Statistics: Run stats gathering jobs to ensure the optimizer works with the latest changes. Gather Updated Statistics: Run stats gathering jobs to ensure the optimizer works with the latest changes.

Even with all precautions, patch failures can occur. Always have a rollback strategy : - Restore from RMAN backup if the patch causes issues. Restore from RMAN backup if the patch causes issues. - Use to revert the patch. Use to revert the patch. - Re-validate system stability before bringing it back into production. Re-validate system stability before bringing it back into production.

- Apply patches first on a test or staging environment before production. Apply patches first on a test or staging environment before production. - Maintain a patching calendar aligned with Oracle’s quarterly Critical Patch Updates (CPU). Maintain a patching calendar aligned with Oracle’s quarterly Critical Patch Updates (CPU). - Keep documentation of all patch activities — patch ID, date, nodes affected, and verification results. Keep documentation of all patch activities — patch ID, date, nodes affected, and verification results. - Ensure adequate disk space and FRA space before patching. Ensure adequate disk space and FRA space before patching. - In RAC setups, apply patches node by node to minimize downtime. In RAC setups, apply patches node by node to minimize downtime.

Patching is a crucial part of Oracle DBA operations that ensures your database remains secure, compliant, and stable. By following structured pre-checks, backup strategies, and post-validation steps, you can apply PSU and RU patches safely without impacting production . Regular patching not only keeps your systems protected but also improves performance and compatibility with Oracle’s evolving ecosystem. For more Oracle DBA insights and step-by-step guides, visit: Want to see how we teach? Head over to our YouTube channel for insights, tutorials, and tech breakdowns: www.youtube.com/@learnomate To know more about our courses, offerings, and team: Visit our official website: www.learnomate.org Let’s connect and talk tech! Follow me on LinkedIn for more updates, thoughts, and learning resources: https://www.linkedin.com/in/ankushthavali/ If you want to read more about different technologies, Check out our detailed blog posts here: https://learnomate.org/blogs/ Let’s keep learning, exploring, and growing together. Because staying curious is the first step to staying ahead. Happy learning! ANKUSH