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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 disks…
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, but…
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, the…
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