The migration process assigns the VDisk an online or offline state based on the states of the source and target managed disk groups. In this case, based on the offline state of the target managed disk group the VDisk that is currently online would have been taken offline. The command cannot be initiated because this action is not supported. There will be an entry in the error log for the corresponding managed disk group.
For each node, note the online or offline state of the source and target managed disk groups. For each node, if one of these two managed disk groups is online and the other is offline, bring online whichever managed disk group is offline. Taking the online managed disk group offline is not recommended because other VDisks might go offline.