Hi Matteo,
You can do something like this:
1Get-UcsServiceProfile -name spName | Set-UcsServiceProfile -BootPolicyName san_boot -Force
2or when you're done...
3Get-UcsServiceProfile -name spName | Set-UcsServiceProfile -BootPolicyName local_boot -Force
That's assuming you've set up a boot policy called san_boot & local_boot, you've got boot luns built, presented, zoned, etc. The -Force just prevents confirmation that you want to change the boot policy setting.
Sage