Server 2003 Migration Gotcha: 32-bit Desktop Applications on Citrix / RDS Print E-mail
Windows 64-bit
Written by Darwin Sanoy   
Wednesday, July 16, 2014 4:28pm

It is never ceases to amaze me how many application compatibility issues I diagnose that come down to challenges running 32-bit software on 64-bit Windows!  Flexera is sounding the same drum beat as the primary application compatibility concern when migrating off of Server 2003 and I have to say I agree.

Ben Hilker of Flexera states:

"Application compatibility due to the shift from 32-bit to a 64-bit operating system is probably the most significant challenge to deal with when migrating from Windows Server 2003 to a more current version like Windows Server 2008 or even 2012 R2." (original article)

True server applications are an obvious consideration when moving from 32-bit server operating systems to 64-bit.  However, many organizations tend to overlook the 32-bit desktop applications running on Citrix or RDS.  

In one case I worked on, a very old powerbuilder application ran solely on Citrix on Server 2003 - it no longer ran directly on a single desktop machine.  The organization had long since completed desktop application testing for Windows 7 64-bit and was mostly completed with their 64-bit desktop deployment.

So 64-bit compatibility was not on anyone's radar when this application moved to Citrix on Server 2008 R2.  The issue manifested itself as the application refusing to open .JPG files attached to the records it kept.  The might procmon with debug symbols was able to isolate the specific call and some googling showed it to be related to the bitness of the application.

As with the 64-bit desktop, the vast majority of applications function very well on the WOW64 subsystem built into 64-bit Windows - the challenging part can be installing and maintaining them where the differences in 32-bit application support creates a bit of a learning curve and the need for a constant awareness of how 32-bit application comprehend the 64-bit OS.  For instance it is common to install the 64-bit editions of runtimes like Java or Oracle client on a 64-bit machine, but forget that the 32-bit version is also needed if 32-bit software is to run on the machine.

So if you are preparing for the journey to rid your company of those last 32-bit Windows 2003 Servers - I recommend you keep an eye out for bitness issues and don't forget to bring along a copy of our ebook / eClass: "Under the Microscope: Deploying and Supporting Applications on 64-bit Windows"