1/ Stop + disable „Microsoft Azure AD Sync“ (ADSync)
2/ Migrate database to new SQL server (CI collation etc, see https://docs.microsoft.com/en-us/azure/active-directory/connect/active-directory-aadconnect-prerequisites)
3/ Restore db owner + permissions for a service account on new SQL server
4/ Backup registry:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\ADSync\Parameters
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSOLCoExistence\CurrentVersion
5/ Update registry with new SQL server/instance name
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\ADSync\Parameters\SQLInstance
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\ADSync\Parameters\Server
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSOLCoExistence\CurrentVersion\SqlInstanceName
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSOLCoExistence\CurrentVersion\SqlServerName
6/ Start „Microsoft Azure AD Sync“ (ADSync)
7/ Check logs + sync manager console
8/ 🙂