Citrix XenApp 5.0 Windows 2003 Hotfix Rollup 4 has new feature enhancement that allows you to give precedence to session sharing over load balancing. Now with this enhancement you can decide to have session sharing override load balancing in your XenApp farm.

In the past when you launched additional applications that are published on the same server, XenApp would try to launch those in the same session if load balancing allowed it. If it didn’t, you would get a new session on another server with a lighter load. The same would happen for a disconnected session. XenApp would try to reconnect you to that disconnected session. If the server load was to high, it would start a new session on another server with lighter load.  This enhancement can be enabled on XenApp 5.0 Windows 2003 with Hotfix Rollup 4.  This can be done by creating the following registry key on your XenApp servers:

32-bit XenApp 5.0 Windows 2003

Path: HKLMSoftwareCitrixIMA

Value Name: OverrideLoadCheck

Type: REG_DWORD

Value: 1 (on) or 0 (off)

64-bit XenApp 5.0 Windows 2003

Path: HKLMSoftwareWow6432NodeCitrixIMA

Value Name: OverrideLoadCheck

Type: REG_DWORD

Value: 1 (on) or 0 (off)

Recreate the local host cache on the XenApp servers the registry change was made on and restart the Citrix IMA service.

Now with this enhancement enabled:

  • Applications launched by users that have an active session join that session rather than going to the least loaded server
  • Applications launched by users that have a disconnected session are directed to the server with the disconnected session rather than going to the least loaded server.

For more information see Citrix Knowledgebase Article CTX126839 – How to Set Up Session Sharing Precedence Over Load Balancing in a XenApp Farm

Enabling this enhancement can be good and bad.  The good side is that additional applications will launch faster and session share with an existing session.  The bad side is that enabling this enhancement could effect server performance.  If the server the session is already running on is overloaded, then this enhancement could cause the server additional performance degradation.  So the question is what’s more important…faster application launches or better session performance?  I leave that up to you.

If you have found this article interesting or if you have any other insights, please feel free to contact me via email.