Modify the shared heap buffer sizes

If you reduce the size of the common or interactive memory, you leave more memory available for non-interactive desktops. However, reducing the sizes of either of these might cause performance problems. Microsoft sets these values by default because their tests show that these are the required values. You are not recommended to change these values.

Reducing the memory used for a non-interactive desktop will allow more desktops to be created. Individual processes that require more memory might be impacted, but most processes will run successfully. If your default non-interactive desktop memory (third entry) is 512, try reducing it to 256. See Modify the Windows registry entries that determine the heap size for how to do it.