In Unibase Imaging, release 7.45i, DMAC allowed users to have up to fifty virtual buffers for decoding images. The Windows operating systems helped us outsmart ourselves. The only advantage of the buffers was speed. We calculated how much memory was real (ram not virtual) and automatically set up buffers to use this memory.

Users would go start another window after starting Unibase Imaging. This would reduce the amount of real ram available and Windows would put the virtual buffer in virtual memory.

Too much virtual for speed or the operating system. Soon the thrashing created multimillion byte virtual buffers which grew but did not shrink. To solve the problem; we added an environment variable which allows the user to limit the number of buffers, usually to three, created regardless of the real ram memory available to the application.