When importing root node keys from a large environment, tw_root_node_key_import may run for many hours before completing. If it is not run using 'screen', the session may timeout, and the import may fail without error or notification. As a result, not all of the root node keys may be imported.
BMC now recommends to run "screen" before running tw_root_node_key_import to prevent this session timeout failure. See https://docs.bmc.com/docs/display/DISCO113/Using+screen.