In this new version we have this feature high availability mode. If all the delivery controller sites fail, the Virtual Desktop Agent(VDA) can be configured to run in high availability mode so that users can continue to use their desktops. With high availability mode enabled, user establishes direct ICA connection with VDA.

By default if communication with delivery controller fails, high availability mode is initiated after 5 minutes which user can configure as per requirement.

With high availability mode enabled, VDA tries to connect to delivery controller for 30 days. But in case it is not able to connect for 30 days, it is then no longer available. Delivery controller should be repaired within 30 days.

High availability can only be used for dedicated desktops, for pooled you cannot configure this feature.

There are two ways in which high availability mode can be enabled:
1) Set the HighAvailability and HaRegistrarTimeout registry keys.

  • Add the following registry entry to HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\VirtualDesktopAgent:
    Name: HighAvailability
    Type: REG_DWORD
    1 = enables high availability mode
    0 (zero) = disables high availability mode
  • To change the time period that the VDA tries registering with the Controller before initiating high availability mode, also add the following registry entry:
    Name: HaRegistrarTimeout
    Type: REG_DWORD
    Value: number of seconds. The default is 300 seconds.
  • Restart the virtual desktop.

2) Provide user ICA file user to directly connect to server. For information on how to create ICA files, see

Some features are unavailable in high availability mode:
• User roaming
• Power management
• Delivery controller-originated policies
• Netscalar gatway and remote access.

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