A client with Oracle 19c on Linux and disappointing performance. Default installation, no tuning. Huge Pages, semaphores, I/O scheduler, THP and security limits: everything that was missing — with the before-and-after numbers.
Friday evening, the night before a go-live. Performance collapses. Using AWR and ASH I found a hidden full table scan in a stored procedure in under ten minutes — and the production release went ahead.
A client where every application user connected as the schema owner with the DBA role. How I restructured the Oracle security model by applying the principle of least privilege — with real SQL, custom roles and Unified Audit.
A client with a 2-billion-row transaction table and reporting queries that had gone from seconds to hours. How I solved it with Oracle partitioning — range, interval, partition pruning and local indexes.
An Oracle production database with no redundancy. A disk failure that brought everything to a halt for six hours. And the CEO's decision to invest in an Active Data Guard architecture with automatic switchover.