Cluster synchronization occurs when cluster-affecting changes are made from SAP Control Center, such as changing security configurations, adding a domain, or changing server listeners.
Domain synchronization occurs when you deploy or undeploy packages or do other administrative operations that affect only a single domain.
Domain and cluster versions are maintained in tables in the clusterdb database. Scheduled tasks running on each SAP Mobile Platform server node periodically check the versions from the database against their own current version, and perform a cluster sync or domain sync as necessary.