There is a SnapManager Migration Guide available for SnapCenter 1.1:
https://library.netapp.com/ecm/ecm_download_file/ECMLP2440302
However, i cannot find an updated one for version 4.0. All I can find is the "Importing Data from SnapManager to SnapCenter" guide which just describes importing backups archived using SnapVault (we use SnapMirror so this doesn't apply to us).
Any suggestions? Does anyone know if a 4.0 version is on the way? Does the 1.1 procedure still work in 4.0?