Hi,
If you change interface form one VDC to another, there in no need to reload, but if you change memory allocation, then a reload is required:
The Cisco NX-OS software reserves the minimum limit for the resource. Changing the minimum limit for IPv4 multicast routing map memory takes affect only after a device reload or a stateful supervisor module switchover
more info
http://www.cisco.com/en/US/docs/switches/datacenter/sw/5_x/nx-os/virtual_device_context/command/reference/vdc_cmd.pdf
HTH