Apart from having all the benefits mentioned above there still remains a question mark whether XenApp 6 is the most stable version that CITRIX have brought in. There still remain so many bugs and glitches in XenApp6 that sometimes the administrators have to pluck the hairs from their head off to get the resolution or a Workaround. Some of the well known issues are as follows:

•XenApp 6 only runs on Windows Server 2008 R2
•Problem with any 32-bit applications
•Schedule Reboot Problem
•Servers undergoing Blue Screen of Death
•Problems while launching applications
•Issues with the Administrative Console

1.1. XenApp 6 only runs on Windows Server 2008 R2

The new Product of Citrix XenApp 6 only runs on Windows Server 2008 R2 (x64 bit Operating System) and not on Windows Server 2003 or Windows Server 2008. So, if a Company want to migrate their existent Citrix environment from XenApp 5 or PS 4.5 to XenApp 6, it is essential to build a whole new XenApp 6 Farm then after a full fledged testing operation migrate all the users to the new Farm. It’s not possible to go into a mixed mode operation which was possible till XenApp 5. No registry twigs or any patches will allow a mixed mode in XenApp 6.

So, before migration to XenApp 6 all the companies need to keep in mind that a new XenApp6 Farm is needed and the previous version is of no use. After Migration to the new XenApp 6 Farm and the old one could either be used for testing purposes or scraped.

1.2. Problem with any 32-bit applications

As XenApp6 only runs on Windows Server 2008 R2 which is a 64-bit OS, there may be some issues when a 32 bit application is hosted on XenApp6. The main issue that can be faced is high memory consumption by a particular session which can go up to 1.8 GB.
Other issues that can creep in are slow performance of the application, low throughput and some latency issues. Even the performance of the Servers hosting those applications can degrade to a considerable extent. The Servers can hang now and then when the load goes up.

For example, the SAP GUI 7.1 is a 32-bit application and when it is published from a XenApp6 Server all the issues mentioned above can come live. So, its recommended to install and publish only 64-bit applications like SAP GUI 7.2 as in our example.

1.3. Schedule Reboot Problem

One of the problems of XenApp6 is that when it undergoes a scheduled reboot if any active or idle session is present in the Server, the Server will not come up freshly after the reboot. It has to be manually rebooted from the VM (in case of Virtual Server) or from the iLOM (in case of Physical Server).

CITRIX have released a Hotfix XA600W2K8R2X64003 which addresses the issue. But, the best way to resolve the issue is to reboot the Servers using the OS policy with a shutdown script which will logoff all the user sessions from the Server before rebooting the Server.

1.4. Servers undergoing Blue Screen of Death

One of the Major issue with XenApp6 is that the XenApp6 Servers can face Blue Screen of Death on a Random Basis. Citrix have already identified two different reasons for which the Servers can undergo BSoD. One of them is for Picadm.sys and the other one is for IMAAdvanceSrv.exe.

Citrix have released two Hotfixes to address the BSoD Issue. XenApp Hotfix XA600W2K8R2X64018 is for Picadm.sys and XA600W2K8R2X64029 is for IMAAdvanceSrv.exe.

Unfortunately, applying the Hotfixes don’t resolve the issue completely, it just lowers down the rate of occurrence.

1.5. Problems while launching applications

There are some loopholes too in XenApp6 which makes it behave weird when it comes to launching the applications. Sometimes it shows Black Screen when a published Desktop is launched or it may pop a message box saying “Remote Computer is Currently Busy” or “A device attached to the System is not working”. Every time the only way is to logoff and relogin after a few minutes which will clear up all the Weird things.

Sometimes XenApp6 cannot clear up some zombie user sessions which prevent the User from launching the same application. The Sessions needs to be cleared before he could further launch the application successfully.

1.6. Issues with the Administrative Console

 There are some intermittent incidents which may occur while an administrator is trying to do some administrative task through the Delivery services Console. Forcefully Logging Off a session or to disconnect a session can sometimes be not possible. Moreover, the data provided in the Console about a particular session can sometimes be incomplete. Usually the application name which has been launched is not shown.

1.7. XenApp 6 doesn’t support MS Access or DB2

Till XenApp 5 the Data stores that were supported were MS SQL Server, MS SQL Server Express, Oracle, MS Access and DB2. But from XenApp6 MS Access and IBM DB2 are not supported as datastores.

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