Answer
Power9 has passed two separate IBM lifecycle milestones, not one. IBM withdrew Power9 from marketing on October 20, 2023, meaning it can no longer be purchased new. Its End of Standard Service date, when IBM stopped developing new firmware, PTFs, and fixes for the platform, was January 31, 2026.
A Power9 system does not stop working on either date. What changes is that new hardware is no longer available and IBM is no longer issuing new code for the platform. Shops still running Power9 in production should have a third-party maintenance contract, a migration plan, or both.