This Ruby example lists the data centers.

# Get the reference to the root of the services tree:
system_service = connection.system_service

# Get the reference to the service that manages the
# collection of data centers:
dcs_service = system_service.data_centers_service

# Retrieve the list of data centers and for each one
# print its name:
dcs = dcs_service.list
dcs.each do |dc|
  puts dc.name
end

In an environment with only the Default data center, the example outputs:

Default

For more information, see http://www.rubydoc.info/gems/ovirt-engine-sdk/OvirtSDK4/DataCentersService:list.