Windows Desktop Heap allocation

The System Architect XT installation sets the Windows registry to allocate enough space for twelve concurrent users. By default, each session of System Architect XT uses up to 37 KB of a single non-interactive Windows Desktop Heap. The System Architect XT installation does not change this setting, but you can change it as necessary as describe below.

In Windows, the amount of Desktop Heap available can be modified in the following registry subkey:

The default value for this subkey usually looks like the following:

%SystemRoot%\system32\csrss.exe ObjectDirectory=\Windows SharedSection=1024,3072,512 Windows=On SubSystemType=Windows ServerDll=basesrv,1 ServerDll=winsrv:UserServerDllInitialization,3 ServerDll=winsrv:ConServerDllInitialization,2 ProfileControl=Off MaxRequestThreads=16

The SharedSection entry in this subkey controls the number of KBs allocated to each of three different types of Desktop Heaps. System Architect XT uses the third value (512) in the SharedSection. In this example, the system will allocate 512 Kb of space for all the System Architect XT sessions to share, which will allow 12 sessions of System Architect XT to be run concurrently.

Modifying this value can impact other applications running on the same computer: before changing it, see:

The System Architect XT web.config file (in the System Architect XT installation folder, usually C:\Program Files\UNICOM Systems\System Architect Suite\SAXT) contains an appSetting entry that must be set to match the value in the registry. The key MaxDesktopHeap should have its value set to the same value specified in the registry. This web.config entry allows System Architect XT to ensure that users do not attempt to start sessions that would cause this allocation to be exceeded.

If you use the System Architect XT Web Service feature, it will be allocated its own instance of the non-interactive Windows Desktop Heap. All specifications described above for System Architect XT also apply to System Architect XT Web Service. The SAXTWebService web.config file also contains an appSetting entry that must be set to match the value in the registry. TheMaxDesktopHeap key should have its value set to the same value specified in the registry. This web.config entry allows SAXTWebService to ensure that users do not attempt to start sessions that would cause this allocation to be exceeded.