The 'transition' is the process of change in planetary leadership of Arrakis from the Harkonnen to the Atreides. This is arbitrated by Kynes, the Imperial Planetologist who is acting as 'Judge of the Change' with power and authority to call shenanigans if the Harkonnen get caught cheating.
“As you wish,” the Duke said. He glanced down at Paul. “Son, this is
the Judge of the Change, the arbiter of dispute, the man set here to
see that the forms are obeyed in our assumption of power over this
fief.” He glanced at Kynes. “And this is my son.”
Dune
Theoretically, the Harkonnen are supposed to arrange for an orderly takeover, leaving in place both equipment and personnel. In reality they do everything they can, short of open malfeasance to make the transition as difficult as possible in the hopes that this will distract the Atreides leadership from the genuine attack that is to be enacted shortly.
”We will have to take it at the point of the sword,“ Leto said. He
turned to Hawat. ”This’d be a good point to report on equipment. How
many sandcrawlers, harvesters, spice factories, and supporting
equipment have they left us?“
”A full complement, as it says in the Imperial inventory audited by
the Judge of the Change, my Lord,“ Hawat said. He gestured for an aide
to pass him a folder, opened the folder on the table in front of him.
”They neglect to mention that less than half the crawlers are
operable, that only about a third have carryalls to fly them to spice
sands–that everything the Harkonnens left us is ready to break down
and fall apart. We’ll be lucky to get half the equipment into
operation and luckier yet if a fourth of it’s still working six months
from now.“