Dhiraj Kumar's Blog

Category: oracle

  • Troubleshooting High gc freelist Waits in Oracle RAC: Root Cause and Resolution

    In an Oracle Real Application Clusters (RAC) environment, batch jobs or maintenance tasks that typically run in minutes can occasionally encounter severe bottlenecks. A common yet elusive culprit is the gc freelist wait event. The Scenario A routine batch job—responsible for disabling and enabling constraints across schemas normally finishes within 1 to 2 minutes. Suddenly,…

  • Oracle RAC Grid Infrastructure Upgrade Failure: When “Downgrade Successful” Isn’t Actually Successful (19c → 26ai)

    When a major-version Grid Infrastructure upgrade fails partway through, Oracle gives you a documented recovery path: the “Online Terminate Upgrade” downgrade procedure. It’s well documented, it runs clean, and it tells you it succeeded. But in a real 2-node RAC test cluster, following that exact procedure left the cluster in a state where CRS simply…

  • Oracle RAC Grid Infrastructure Upgrade from 19c to 26ai (23c) with Real Logs

    Upgrading Oracle Grid Infrastructure (GI) from 19c to 26ai (23c internally) is a critical task for RAC environments. While Oracle provides documentation, real-world execution often requires additional clarity. In this guide, I will walk through a complete step-by-step upgrade of a 2-node RAC cluster, using actual commands and logs from a real upgrade scenario. Step…

  • ASM Instance Termination After OCR Restore 19c/26ai

    After a storage migration activity, a two-node Oracle RAC environment experienced Oracle Cluster Registry (OCR) corruption. Although OCR was restored successfully on a newly provisioned disk, ASM instances repeatedly terminated with internal errors. Further investigation revealed that the issue was not related to Oracle software or OCR restore procedures, but to an underlying disk visibility…

  • Oracle Database 26ai – An AI-First Database Platform

    Oracle Database 26ai represents Oracle’s next-generation, AI-first database, where artificial intelligence capabilities are natively embedded into the database engine rather than delivered as external or bolt-on services. This is not just another version of the Oracle Database—it is better described as a learning and enablement platform for AI. Oracle Database 26ai is specifically designed for:…

  • Oracle Database Appliance (ODA) 19.29 Patching: Understanding the Two-Stage Patching Process

    Oracle Database Appliance (ODA) patching is a critical operational activity to ensure system stability, security, performance, and long-term supportability. With ODA 19.29, Oracle follows a two-stage patching procedure. In this article, we will walk through the two major stages of ODA 19.29 patching and provide the required commands. Why ODA Patching Is Divided into Two…

  • Oracle Grid Infrastructure (GI) 19c Installation and RU Patch 19.28

    Note:Please follow the steps below carefully.You can skip any step if it’s already completed in your environment.Modify paths and variables as per your setup. 1. Delete Existing Oracle Files and Directories Before starting a clean installation, remove any previous Oracle GI installation traces. 2. Create GI Software and Base Directories Create the necessary directories for…