I recently upgraded some of my Hyper-V host servers to 2016 as well as DPM (both OS and DPM version to 2016).
So far everything has gone fairly smooth
Upon updating the host servers, I began to shut each VM down and upgrade their "Configuration Version" from 5.0 to 8.0 in Hyper-V. Then I would go remove them from DPM and re-add them to change it to the RTC type backup.
After doing this, all my VMs are backing up properly using the new RTC backups in DPM, except 1 VM, a DC server.
I have multiple DCs which I have not touched yet (still version 5.0 on a 2016 Host), and they are backing up fine in DPM
The first DC I changed from version 5 to 8 and then removed from DPM to add it back as RTC, won't backup.
Checking the VSS logs inside the DC, I am getting this error
lsass (536) An attempt to open the file "\\?\Volume{fa1a82fe-41bb-4eed-96e8-604d2e17669d}\Windows\NTDS\ntds.dit" for read only access failed with system error 32 (0x00000020): "The process cannot access the file because it is being used by another process. ". The open file operation will fail with error -1032 (0xfffffbf8).
DPM Server
OS: 2016
DPM Version: 2016 5.0.247.0
Hyper-V Host Server
OS: 2016
DPM Agent Version: 5.0.247.0
VM
OS: 2012 R2
Role: DC