The full device designation at the console level for a disk device is something like dka100.1.0.1.8.   The Avanti firmware allows device names to be abbreviated as long as they remain unique.  For example, both boot dka200 and boot dka2 would be valid commands.  If a device name is not unique, a boot or set bootdev_dev will generate a device ddvu is ambiguous warning.  This problem is likely to be encountered when trying to set DKA100, DKB100, or DKC100 as the boot device on a wide controller where DKA1000, DKB1000, or DKC1000 is also present.

To make DKA100 a unique device name, add a dot(.).  Thus, "boot dka100" becomes
"boot dka100.".