Oracle 19c Database Health Check Script – Complete Oracle DBA Guide Maintaining a healthy Oracle Database is one of the most important responsibilities of an Oracle Database Administrator (DBA). A proactive database health check helps identify performance bottlenecks, storage issues, invalid objects, tablespace utilization, backup status, and database availability before they become critical problems. In this article, you'll learn how to create and use an Oracle 19c Database Health Check Script that collects essential database information in a single execution. This guide is designed for Oracle DBAs, System Administrators, Developers, and IT Professionals who want a simple, effective, and reusable script for daily database monitoring. What is an Oracle Database Health Check? An Oracle Database Health Check is a routine assessment of your database environment to verify that critical components are operating correctly. Rather than waiting for users to report problems, D...

ORA-28040: No Matching Authentication Protocol – Complete Oracle Database Troubleshooting Guide The ORA-28040: No Matching Authentication Protocol error is one of the most common authentication issues encountered after upgrading an Oracle Database, Oracle Client, or middleware application. It typically appears when an older client attempts to connect to a newer Oracle database that no longer supports legacy authentication protocols. This guide explains everything you need to know about the ORA-28040 error, including its causes, how Oracle authentication works, troubleshooting techniques, multiple solutions, best practices, and preventive measures. Whether you are an Oracle DBA, System Administrator, Developer, or Infrastructure Engineer, this article provides a practical, production-ready approach to resolving the issue safely. What is ORA-28040? The ORA-28040 error indicates that the authentication protocol used by the Oracle client is not compatible with the authenticat...

ORA-27101: Shared Memory Realm Does Not Exist – Causes, Troubleshooting, and Solutions The Oracle error ORA-27101: Shared Memory Realm Does Not Exist is one of the most common startup and connection errors encountered by Oracle Database administrators. It typically appears together with ORA-01034: ORACLE not available , indicating that the client cannot locate or attach to the Oracle instance's shared memory segment. Whether you are administering Oracle Database on Linux, UNIX, or Windows, understanding why this error occurs is essential for minimizing downtime and restoring database availability quickly. In this guide, we'll explain what the error means, its common causes, and how to diagnose the underlying problem before applying the appropriate solution. Understanding the Error A typical error message looks like this: SQL> connect / as sysdba ERROR: ORA-01034: ORACLE not available ORA-27101: Shared Memory Realm Does Not Exist Linux-x86_64 Error: 2: No suc...