Some of my users were complaining that an application is much slower now on XenApp 6.5 than it was on Presentation Server 4.5

I did some digging into what they were doing and basically from the application the user would browse to a .dat file on a windows server 2003 file server and the application would read the file.  Well this process would take minutes on XenApp 6.5 when it used to take less than 20 seconds.


I decided to take a packet capture from each environment when this process was going on and I found something very interesting.  The size of the packets on the old environment was 4K and on the new environment the size of the packets were 512bytes!  Also I noticed in the packet capture what was different was Opportunistic locking was disabled on the XenApp 6.5 environment.


I found a reg key in windows called "OpslocksDisabled" and the value was set to 1 on the Windows 2008 R2 servers.  Once I set this reg key to 0 and rebooted the XenApp 6.5 server I ran the process again and it was fast once again!  I took a packet capture and the packet captures were identical now!


The reg key is located in the following location:


OplocksDisabled REG_DWORD 0 or 1


0 is the way to go if your file servers are server 2003 (SMB 1.0)