This is a runtime upgrade specific to the launch of the People Chain and takes place in two steps:

1. Immediate upgrade authorization of the Relay Chain to v1.2.7. This allows anyone to call the reap_identity function, which will remove the identity from the subs and reserve the new amount on the People Chain.
2. Scheduled upgrade of the People Chain 3 days (43,200 blocks) later that unblocks calls to allow public use. This will give a three day window to migrate all identities.

Release notes are in v1.2.7 from the Fellowship.

This is steps 2 and 3 of the plan outlined here.

Enactment is set for 25 July.