A library AI rack must replace dual PSUs over a maintenance window. What ordering rule protects continuity?

A library AI rack replacing dual PSUs over a maintenance window must order the work so the node never loses both power feeds at once. Domain 5 power-FRU sequencing protects civic library inference continuity by always retaining a live qualified supply during the procedure. Dual replacement is two sequenced single replacements, not one simultaneous pull, and redundancy LEDs or management power status must confirm the first new supply before the second comes out. Unplugging both feeds first to create a clean slate guarantees an outage and removes redundancy by design. Replacing PSUs in random order without watching redundancy LEDs or management power status can accidentally leave the node on zero healthy feeds mid-swap. Removing the healthy PSU first to test failover theatrically is an unnecessary risk when the maintenance goal is continuous power, not a staged blackout. Exam caveat: label feeds and follow chassis LED or management power status after each step so the second removal only happens once the first new FRU is verified online. Operational check: during the library window, replace one PSU, confirm redundancy restored, then replace the second; never open both feeds concurrently, and record power health after each step.