How to Improve VDI Logon Times

Keep your house tidy!


It only takes a mouse click to break an environment – and recently I found myself trawling through log files to investigate slow logon times with VMWare DEM – the root cause was, as always, frustratingly trivial – a deleted AD group that was still being referenced in the DEM config,  but the steps taken to identify this can help you improve your VDI logon times across your estate (…assuming  your our employer cares about this!). The below principles can be used in any VDI environment with a profile management tool in place.

I’ve split this into 2 sections. The first section How to troubleshoot a logon issue with VMWare DEM includes the actual steps taken to fix aforementioned issue. The second section 5 Tips to Improve VDI Logon Times offers a few ideas to consider in your environment.

How to troubleshoot slow logon with VMWare DEM

  1. First we need to enable granular logging so we can see what is happening during the logon process. For VMWare DEM you can do this by creating a text file named FlexDebug.txt and copy this into the Archive\Logs folder of the affected user.  At logon, FlexEngine service reads the flag text file and logs at a more granular level to the FlexEngine.log file. Deleting the .txt file will revert your logging level back to INFO (or however it is configured in your DEM GPO).

Turn on debug logging in Profile Unity

Turn on debug logging in VMware DEM

2. Log the user out of any open desktop sessions, then delete their FlexEngine.log file so we have a clean log to work with.

3. Log them back on. Once the logon cycle completes, read through the timestamps of logon events and look for gaps of more than 1 or 2s.

Example 1

In total, the below log file shows a gap of 28s where DEM was stuck trying to process erroneous data. The first event is a failed AD group lookup that wasted around 12s over 2 events. The AD group had been deleted from AD, but hasn’t been removed from the UEM config settings.


How to quickly identify a bad settings in your DEM config:

If you’re having trouble locating the offending setting in the GUI of DEM Management Console, then save time by searching the .ini config files directly:

  1. Browse to your UEM Config folder.
  2. Use windows explorer search bar and type content:  to search for whatever text/setting/error/AD group/value is failing to process. This will search the contents of the .INI config files for your DEM installation and quickly identify where your problem lies.


Example 2

Citrix registry value ‘LogOffCheckSysModules’ exists, but does not contain ‘FlexEngine.exe’

This error is caused by an AppVolume package (Adobe Professional) which created the above value in HKLM registry tree. Updating the AppVolume package and deleting the above registry key fixed this.


Issues like these cause overhead on your service desks, remember to keep your house tidy and have regular check-up’s on your logon times. 

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