What is the setting of God Emperor of Dune by Frank Herbert?

God Emperor of Dune is set, like the three preceding Frank Herbert novels, Dune, Dune Messiah, and Children of Dune on the planet Arrakis, whose official name is shortened to Rakis. The unofficial name, Dune, is no longer applicable, for after 3,000 years, only a tiny patch of desert remains, too small even to support the giant sandworms responsible for creating melange spice.