Yep, that is the command, no sz registrar.
The registrar is introduced on request of customers that want to easily let the switch know on which IP or FQDN the management platform is (vSZ/SZ).
With version c it is standard enabled, and with ca, it is standard disabled, with d it is enabled again by default, and you can use the no sz registrar to disable it.
The same system is used on AP's for finding the controller.
regards
Martin