What is the difference between deferred and concurrent firmware updates?

Deferred firmware packages can be uploaded and staged to the system while it is operational - this is the concurrent delivery aspect referenced in the choice. However, because deferred updates modify core internal program code that cannot be safely replaced while active, the new code does not become effective until the next system IPL, which is what distinguishes it from a fully concurrent firmware activation.

Concurrent firmware updates do not require all LPARs in a frame to be updated simultaneously; they can be applied while partitions remain active without requiring coordinated downtime across the entire frame.

Deferred firmware does not require a system outage to be loaded or staged onto the system; the delivery phase happens while the system is running, and only the activation step requires an IPL.

Concurrent firmware is not restricted to minor microcode fixes; the classification refers solely to whether the update can be activated without an IPL, not to the scope or significance of the changes included.