A newly created business record failed with ORA-00001 on a primary key. That was unexpected because the application generated the key from an Oracle sequence. The log resolved the contradiction: the generated value already belonged to an older row that had arrived with the migrated data.

This was …

A browser request returned HTTP 200, yet the response body was empty and the page showed no data. The status code looked successful, but the backend log told a different story: mapped SQL had failed with ORA-00904 while calling WM_CONCAT.

The repair was not a global text substitution. String …