SWPUSEUMB
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  Function : Enable or disable the use of UMBs by the swap system.

  Syntax   : lValue = SWPUSEUMB(lFlag)

  Return   : The previous setting

  Default  : Enabled

  This function enables or disables use of UMBs (upper memory blocks) for
  the resident kernel. If available, and their use is enabled, the
  resident kernel which remains in memory during execution of the child
  process will relocate itself into a UMB, freeing up slightly more
  memory.