DPM 2019: Error 40002 – The VHD containing the replica or one of its snapshots could not be mounted or unmounted
This error was fixed for DPM 2016 in Update Rollup 7. Please fix this for DPM 2019 now, and not make us wait for Update Rollup 1 (Q3 '19 on the roadmap). Neither host nor client has anything to do with VHD's and this error still occurs daily.

The error 40002 could be reported in multiple scenarios of VHD mount and unmount failure.
Here are more details -
WMI Out of memory (Fixed with UR7 for DPM 2016 and already part of DPM 2019 RTM):
One of the top scenario where we observed the 40002 error is due to WMI out of memory. In a scenario, where you see 40002 error in DPM Console and at the same time you may see WMI-Activity error event ID 5858 logged with Result code 0×80041006. This code translates to “not enough memory for the operation’. To address this issue, with DPM 2016 UR 7 we increased the default WMI memory limit from 20MB to 60MB by adding registry keys (details below). This change is already part of DPM 2019 RTM.
If you still see the same failure, the work around could be to increase this limit a bit more. But if the issues persists, there could be more reasons why the calls to WMI might fail. It could be due to inadequate OS resources causing WMI to perform slow or the degraded performance of underlying storage. Our team is investigating further on how we can isolate these issues.
Registry Key Details:
Reg Key : HKLM\SOFTWARE\Microsoft\Wbem\CIMOM
Value: High Threshold On Events (B)
Data (String) : 60000000
Reg Key : HKLM\SOFTWARE\Microsoft\Wbem\CIMOM
High Threshold On Client Objects (B)
Data (String) : 60000000
Sparse file issue with Windows Server 2016:
If this issue is specifically seen, when DPM 2019 /2016 is installed on Windows Server 2016, please check if event ID 27268 is logged in the Hyper-V-VMSS logs with the description as “Virtual hard disk files must be uncompressed and unencrypted and must not be sparse”.
To resolve this issue , install the latest updates for Windows Server 2016.
If you are still experiencing high frequency of this error, please reach out to our customer support team to troubleshoot further.
72 comments
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Anonymous commented
We have still this errors, looks like these solution not working!
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Anonymous commented
Confirmed. VHD mount error still persistent!
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Sunil Dahiya commented
We have similar issues with multiple customers - have to reboot DPM/MABS servers after jobs are failing with 40002 errors. Any fix for this?
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Jason commented
Still an issue as of Dec 4 2020
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Markus Eling (ACG) commented
Mr. Product Owner,
are you still alive? Please give us a sign and kindly let us know about your plans to resolve this problem!
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[Deleted User] commented
Here is the same error with DPM 2019. The DPM server has to be restarted every day so that it can write backups again. useless. DPM2012 works perfectly, but without REFS
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Anonymous commented
this is a bad issue,and now it's already not fixed.
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Paul Anderson commented
I'm having this exact same problem in Microsoft's hybrid Azure Backup / DPM product - MABS DPM v3. We've rebuilt it 4 times with Microsoft on different hardware, applied UR1 and applied all the WMI, registry and other workarounds to no avail. We've had it for 8 months now. I've got over 10 years' experience implementing and managing enterprise backup solutions and have never used anything worse.
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DG commented
The Registry-Fix doenst work. DPM 2019, SRV 2016 and SRV 2019.
Open for more than a year and still no solution.
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Anonymous commented
Confirmed. VHD mount error still persistent!
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JP commented
Confirmed. VHD mount error still persistent!
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Markus Eling (ACG) commented
Unbelievable! Do you anyhow pay attention to user problems or do you really rely fully on automated bug search and fixing? Do we write here with some bot in alpha stadium as well perhaps?
Release notes of UR2 for DPM2019 again contain just one word about this issue. What are your plans for DPM? Not that there's any hope for this scrappy piece of software...
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David Randall commented
Just in case it may work for someone else, we managed to resolve a case of this on 2019 UR1, after all the above failed, by simply moving the local storage location from one modern storage pool to another one.
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JP commented
VHD mount problems not on the fix list RU2 SCDPM 2019?
Are you serious??? This is ridiculous.
We add Veeam to our investment plan.DPM is an obsolete, outdated and slow solution full of bugs that you are not able to solve for many years!
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Anonymous commented
So after upgrading to ur1 and adjusting the wmi as above the issues persists, however, we have found running a dpmsync -reallocatereplica saves us needing to reboot the server fully.
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mah commented
@Mike Jacquet: Thanky you! the WMI Quota increase seamed to fix the mount problems for us, DPM runs now mutch smoother. Altough there is still room for improvement regarding the ReFS Storage performance, al least it's now stable. We're using DPM 2019 UR1 and Windows Srv. 2016 Patchlevel 2020-05
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KimP commented
SCDPM Team. Please come up with a fix for this ASAP. SCDPM2019 UR1 users are experience this issue. Please do something!
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Daniel commented
We do have same Issue with 40002 here as well. Mikes Fixes didn't help.
We do face this Issue now for about 2 Years i believe?! A support case with Microsoft didn't help - they just asked for some Logs and asked some Questions about Setup, we answered ,no more reaction. After a Question About Status they asked for same Logs and same Questions about Setup again which we answered again and so on and so on....after 3 or 4 couple of times we gave up.
Normaly this would be the Point, where we would switch to a product with support that would work and would deserve the Notation "Support". Sadly as Civic Administration we are not able to spend Money for another product, when we already spend Money for this (and it is sadly part of our License pack, so we Need to pay and so to use it). After 2 Years with at least 15-20 Minutes additional per Day to have a look for our backup and to get it back to work i am at the Point, where i won't recommend that solution any time again.
A Backup is the one Thing that you Need to work reliable as well as it is mandatory by laws. I have absolutely no more understanding for Microsoft that they do ignore this Issue for this long and leave their customers without help. It's a shame for this big Company!Btw.: DPM 2019 10.19.260.0 with Server 2019 (latest Patchlevel)
The interessting Thing is, that we do have 2 DPM-Servers on 2 different Locations with same Patchlevel. The one where our workmade didn't Change from NTFS to REFS is working. So cause of this i would suppose, there is no WMI-Problem, there is only a REFS Problem and this is for about Years… -
Anonymous commented
DPM 2019 ver 10.19.260.0. I have made all of the registry tweaks and wbemtest changes and we are still getting the ID:40002 VHD mount unmount errors. I also staggered the protection group times to have at least an hour or two between and still no luck. I'm hoping for a real fix for this, it's been going for way too long.
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SimSim commented
DPM 2019 all updates applied. The VHD containing the replica or one of it's snapshots could not be mounted or unmounted. (ID 40002)