Multi Monitor Screen Memory Settings override

The Maximum amount of memory that can be used for a Session's graphics in XenApp 4.5 via the AMC console is 8192 KB , This can however be overridden with a registry tweak.

To override the 8192KB limit ensure the server is not set to pick up Farm settings and then set the following registry key to the desired size

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\Wds\icawd\thin16
Key : MaxLVBMem

The server will require a reboot for this setting to take effect.

Formula for required Memory
To Calculate the Memory (MaxLVBMem) required use the following formula

M=X*Y*Z

X-Width of the ICA session window
Y- Height of the ICA session window
Z-Color Depth of the ICA session window (where 1=8 bit 2=16 bit 3=24bit)
M-Session Graphics Memory Required

Example (2 screens at 1280 x 1024 resolution 2560 x 1024 x 2 = 5242880 )

Session Pool Size
Be warned that its recommended to review the sessionpoolpage if the above value is changed. The MaxLVBMem should be no greater than 40% of the sessionpoolpage size.
This size is set in the following registry value

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management

No. Of Monitors
The number of monitors used does not really matter, its just a matter of supporting the total resolution that is required for the width of all those screens (eg 4 x 1280 = 5120 for 4 screens)

Further Information
This information was gathered from citrix Article ctx115637 , this article also contains more detail than is posted here.