This article describes how to set up Session Sharing precedence over Load Balancing on a fully loaded XenApp server.

Background

Citrix PSE450W2K3R05 introduced the following enhancement which is described in the hotfix rollup pack read me:

“This feature enhancement allows you to give precedence to session sharing over load balancing. With this enhancement:

• Applications launched by users that have an active published desktop session join that session rather than being routed to the least loaded server.

• Applications launched by users that have a disconnected published desktop session are directed to the server with the disconnected session rather than being routed to the least loaded server.

To enable this enhancement, you must set the following registry key:

On 32-bit Windows:

HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\IMA
Name: OverrideLoadCheck
Type: REG_DWORD
Data: 1 (on); 0 (off)

On 64-bit Windows:

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Citrix\IMA
Name: OverrideLoadCheck
Type: REG_DWORD
Data: 1 (on); 0 (off)
[209995]”

Instructions

To set up Session Sharing Precedence over Load Balancing on a fully loaded XenApp server, complete the following procedure:

1. Run the following command from a command prompt on a XenApp Server to locate the Zone Data Collector in your farm:

   QFARM

   The list of servers in the farm are displayed as shown in the following screen shot:

   

2. The Zone Data Collector is the server listed with the letter D after its network address. Open the registry editor on the Zone Data Collector and navigate to the following registry key:
   On 32-bit Windows:

   HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\IMA

   On 64-bit Windows:

   HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Citrix\IMA 

   Caution! Refer to the Disclaimer at the end of this article before using Registry Editor. 

3. Create a new DWORD value called: OverrideLoadCheck.

4. Set the value to 1.
   

5. Restart the IMA Service on the server after creating the value to activate the change. It is also recommended to recreate the local host cache on the server by running the dsmaint recreatelhc command.

Important! Apply the preceding tasks on all servers that may become Zone Data Collectors. To identify these servers, check the election preferences in the farm Zone Properties. These settings can be found by using the Citrix XenApp Advanced Configuration console and navigating to the farm properties and selecting the Zones option.

On each XenApp member server of the farm, set the following Seamless Exception Flag: DISABLE LOAD CHECK
Value: 0x100

Note: By default, Load Balancing takes precedence over Session Sharing on a fully loaded server. New connections are routed to other less busy servers rather than having their sessions shared with existing connections. Setting this Flag allows session sharing of connections on fully loaded servers. Without this Registry Value set, or setting this value to 0x0, retains the default Load Balancing behavior.

To configure a Seamless Flag, create the value SeamlessFlags, and then specify a Value corresponding to one or more of the following choices:

Note: If Seamless Flags are also configured in the environment, refer to the following Citrix article that explains how to set multiple Seamless flags:
CTX101644 - Seamless Configuration Settings.

Note: The flag is only applied to new sessions.

Restarting the XenApp server is not required after setting the Seamless Flag.