Managed Object References

A managed object reference (moRef) is actually a handle and not the managed object itself. While it is certain that a moRef always contains a unique value, the unique value is only relative to the instance of vSphere to which you are connected. For example, if vCenter Server manages a cluster of ESXi hosts, each ESXi host maintains its own managed object reference namespace and the vCenter must maintain a managed object reference namespace representing all of its servers. So when an ESXi host is represented by a vCenter, the vCenter must ensure that the managed object references are unique. The vCenter accomplishes this by creating unique managed object reference names inside its own namespace, which differ from the names that ESXi uses for the same managed objects.

A vSphere instance (vCenter or ESXi) tries to keep the moRef for a virtual machine consistent across sessions, however consistency is not guaranteed. For example, unregistering and reregistering a virtual machine could result in a change to the moRef for the virtual machine. Thus, it is a bad idea to store a moRef and expect it to work correctly in future sessions, or with a different vCenter Server.