Applies To:
  • CitectSCADA 1.00, 1.01, 1.10, 1.11, 2.00, 2.01

When running in real mode NetBIOS, Windows requires a Network Heap. This heap is controlled by the option [386Enh] NetHeapSize in the SYSTEM.INI file. As the network is loaded, Windows will use more network heap, and under high loading it may run out of Network Heap. If this happens, Windows will display a blue screen telling you to increase the size of the Network heap. However under some conditions when Windows tries to display the blue screen message, it may crash the Computer. You will have to power down the computer, then restart.

If you use Windows for Workgroups 3.11, and Citect is using the NetBEUE protocol, the network heap is not used, as the protocol runs in protected mode. This problem may occur with Windows 3.1, Windows for Workgroups 3.1 when running the Novel Netware NetBIOS protocol or other real mode NetBIOS protocols. 

If your computer crashes under network loading, or you get the blue screen error message, increase the network heap. Try setting the heap to 64. If you upgrade to Windows for Workgroups 3.11 you may use protected mode protocol stack which will bypass the network heap, so this is also a solution.