<BASEDIR>/IP/smarts/bin/sm_tpmgr -s <domain name> --load-conf=<conf file>
However, the --load-conf command will not work for the discovery.conf file.
The changes made using dmctl will take effect immediately, but will not persist through a domain restart. However, the changes in discovery.conf will persist through the restart. You can test a change by making the change temporarily using dmctl. If the change turns out positive, you can make the change permanent in discovery.conf.