If a server has been offline for a period of time longer than the replication purge delay, the dsreplication initialize command must be performed to bring the replica into sync with the topology.
Server startup is the only time missed changes are detected. A missed change is a change that the replica detects that it needs, but which cannot be found within any other replication server's replicationChanges backend (stored in the path server root /changelogDb). If missed changes are detected, the server enters lockdown mode, where only privileged clients can make requests. Any other server that is not missing changes can be used as a source for dsreplication initialize.
If a manual backup and restore of the server is required, then the following steps are equivalent to dsreplication initialize.