The flag Thomas is referring to seems to be the flags property in RDSK block, see section "6.1 What is the Rigid Disk Block ?" at
http://lclevy.free.fr/adflib/adf_info.html.
Usually the flag is set to 7 (bit 1+2+4) in many common cases meaning:
1 No LUNs exists to be configured greater than this one at this SCSI Target ID
2 No target IDs exists to be configured greater than this one on this SCSI bus
4 Disk indentification valid
But I can't find any option in rdbtool to change it.