dbaliw

Ghost in the Datafile: Fixing “Empty Block” Corruption in Oracle

A common frustration for DBAs occurs after identifying a corrupted index or table. You drop the object, expecting the error to vanish, but RMAN backups still fail and Data Guard continues to report a gap. Even though the block is no longer part of a segment, it remains “physically” corrupted in the eyes of theContinue reading “Ghost in the Datafile: Fixing “Empty Block” Corruption in Oracle”

Oracle 26ai: Out-of-Place Database Patching Explained

Patching a database often means turning it off, which is a problem for businesses. In Oracle 26ai, there is a great new feature called Local Rolling Out-of-Place Patching. This feature helps you move your database to a new, patched “Oracle Home” on the same server without stopping database (or short downtime). Here is how itContinue reading “Oracle 26ai: Out-of-Place Database Patching Explained”

Exadata Snapshot PDB Clone with ACFS

When working with Exadata, there are several ways to create snapshot PDB clones. The main options are: Each one works well, but the best choice really depends on your environment and what you need. Exascale Clone This is clearly the most modern solution. It’s fast, simple, and designed for large environments. But in reality, notContinue reading “Exadata Snapshot PDB Clone with ACFS”

ACFS Replication Background Process Stopped After Upgrade to 23ai

If you recently moved from Oracle 19c to Oracle 23ai, you might find your file replication has stopped. Your status shows “Stopped”, and no matter how many times you try to start it, nothing happens. The Problem: The “SCAN” Name In the old version (19c), replication usually connected directly to a specific server’s name orContinue reading “ACFS Replication Background Process Stopped After Upgrade to 23ai”

Deinstalling Oracle Grid Home in Oracle 23ai: Step-by-Step Guide

In Oracle 23ai, the procedure for deinstalling an Oracle Home or Grid Infrastructure Home has not changed compared to previous releases. The standard deinstall utility is still used, and the process remains straightforward. In this article, I will walk through the real procedure I followed to remove an Oracle Grid Home in Oracle 23ai andContinue reading “Deinstalling Oracle Grid Home in Oracle 23ai: Step-by-Step Guide”

Understanding Disk Rebuilds After Replacement in Exadata Compute Nodes

When a disk fails in an Exadata compute node, it should be replaced as soon as possible. Compute node disks are typically configured with RAID-5, which can tolerate only one disk failure. ⚠️ Important: RAID-5 does not create two copies of your data. It stores only one copy, with parity distributed across the other disksContinue reading “Understanding Disk Rebuilds After Replacement in Exadata Compute Nodes”

Partitioning in PostgreSQL vs Oracle

A customer who had migrated from Oracle to PostgreSQL several years ago recently reported a serious performance regression. A critical table—now holding over 700 million rows—had become extremely slow when filtering by date. As an DBA, I approached this from an Oracle perspective: partition pruning, local indexes. PostgreSQL partitioning is broadly similar to Oracle’s, butContinue reading “Partitioning in PostgreSQL vs Oracle”

When the Clustering Factor Strikes: How a “Perfect” Plan Turned into a 9-Second I/O Nightmare

This wasn’t a theoretical exercise—it was a real-world performance issue that left the database paralyzed.Let’s start with the global stats: The database wasn’t working—it was waiting.Over 90% of the query’s elapsed time was spent on I/O waits, meaning the database was stuck reading data from disk. Step 1: The Execution Plan At first view, theContinue reading “When the Clustering Factor Strikes: How a “Perfect” Plan Turned into a 9-Second I/O Nightmare”

Streamlit : Making Your Enterprise Knowledge Assistant AI Accessible

Last time, I built a working enterprise knowledge assistant in Python using RAG + OpenAI + Chroma. It could read documents, answer questions, and even remember chat history. Today, I’m taking it a step further: giving it a friendly web interface. Instead of typing commands in a terminal, employees can now interact with the assistantContinue reading “Streamlit : Making Your Enterprise Knowledge Assistant AI Accessible”