As soon as the zone files of a dynamic DNS server are edited during operation, the next time the bind is started, the error message "journal rollforward failed: journal out of sync with zone" results and the changes to the zone files may not have been applied.
To allow a manual change of the zone files and to avoid the path via nsupdate, the rndc command exists with the options freeze and thaw.
For a zone file to be edited, this zone is frozen with the freeze option. This
# rndc freeze db.example.org
# rndc freeze 21.156.189.in-addr.arpa
will freeze both the db.example.org zone and the reverse lookup zone 21.156.189.in-addr.arpa. The freeze option temporarily disables the automatic updates so that the journal files can be transferred to the zone files. Once the zone files have been edited, the thaw option enables the dynamic updates again, and Bind can reread the modified zone files.
# rndc thaw db.example.org
# rndc thaw 21.156.189.in-addr.arpa