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Job Fails to Start Due to Timeout Caused by Desktop Heap Allocation Failure

KB ID: 1909
Product: Veeam Backup & Replication
Veeam Agent for Microsoft Windows
Version: VBR - 7 and up | VAW - 2.x and up
Published: 2014-07-29
Last Modified: 2023-04-13
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Article Applicability

The timeout error displayed in Veeam Backup & Replication can be caused by various factors. This article specifically addresses a scenario where the Windows OS experiences a 'heap allocation' failure.

Please note that the solution provided in this article is only applicable if you have identified Event ID #243 in the Windows System Event Logs (eventvwr.msc). If this event is not present, this article may not provide a relevant solution.

Challenge

In Veeam Backup & Replication, if more than 100 jobs are running simultaneously, and the user attempts to start more jobs, they may fail to start with the following error message: 
Error Job <JobName> cannot be started. SessionId: <UUID>, Timeout: [361 sec]
A Veeam Agent for Microsoft Windows backup job may fail with: 
Managed session <UUID> has failed
In the Veeam Agent for Microsoft Windows service logs (Svc.VeeamEndpointBackup.log) following errors are found: 
Error Job <JobName> cannot be started. SessionId: <UUID>, Timeout: [361 sec]
Error Job [Infrastructure update] has failed to start. Timeout expired (6 minutes). SessionId: <UUID>
The following event is found in the System event logs: 
Log Name:      System
Source:        Win32k
Event ID:      243
Task Category: None
Level:         Warning
Keywords:      Classic
User:          N/A
Computer:     
Description:
A desktop heap allocation failed.

Cause

By default, Veeam services are run as the LocalSystem account. As a result, all processes are started under NT AUTHORITY\SYSTEM context. If the Windows OS is running out of Desktop Heap memory, new processes can't be started. 

Solution

The Desktop Heap size must be increased via a registry modification.

Because this change will affect the desktop heap of all services (also known as non-interactive window stations), do not make the new value larger than necessary.
 

  1. Open Registry Editor (regedit) and navigate to
    HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\SubSystems
  2. Within the SubSystems key will be a Value named Windows.
  3. Double-click on the value named Windows.
RegValue
  1. Find the part labeled "ShareSection=" followed by three sets of numbers separated by commas.

    The third SharedSection value is the size of the desktop heap for each desktop that is associated with a non-interactive window station. The value is in kilobytes (KB).
  2. Modify the third value, and change it to 2048.
    Do not modify any other values.
SharedSection
  1. Click OK to commit the changes.
  2. Reboot the machine.
The steps provided may not always resolve the heap issue. If a third-party service causes the desktop heap memory leak, the problem may return several days\weeks after OS restart. If this occurs, we recommend contacting Microsoft support for low-level debugging assistance.

More Information

Starting with Server 2012 R2, Microsoft has changed the core logic of the heap memory management system, and publicly available tools used with previous versions to check per process head usage are incompatible. If you encounter the Veeam error listed in this KB and Event ID# 243 is found in the event viewer, we advise opening a case with Microsoft support to request assistance tracking down any service memory leaks.
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