Hello,
Some news, we will use the latest upgradetools (version 997000802) to export import our SMS. The new version will do an import with a cloning like SK sk180631 with the same drawback except for the domain name and IP address.
The biggest issue is the rebuild of the Gateway network part (interface, IP and topology) and the SIC, so to ensure a smooth transition we will change the IP address for the new domain and migrate one by one all the cluster.
By adopting this approach, we limit the impact on production and the risk of losing a GW, but we add extra work for the integration teams, who will have to make the policy changes twice until the end of the migration.