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”
Tag Archives: sql
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”
Benefits of Zstandard Compression in Oracle 23ai HCC
In Oracle Database 23ai, significant improvements have been made to Hybrid Columnar Compression (HCC), with the default compression method now utilizing Zstandard (Zstd) instead of the previous algorithms, zlib and bzip2. But what exactly is Zstandard, and how does it differ from zlib and bzip2? Zstandard is a lossless data compression algorithm developed by YannContinue reading “Benefits of Zstandard Compression in Oracle 23ai HCC”
Oracle DBA Insights 