DMSMS
Beginner
When the companies that make a part stop making it, but the machine that needs it is still in use.
Novice
Diminishing Manufacturing Sources and Material Shortages: the loss, or coming loss, of the companies or materials needed to keep making a part.
Expert
A program-level discipline in the U.S. Defense Department. For chips it means lifetime buys, redesign onto a newer process, emulation, or portable RTL and documentation that let a part be rebuilt decades later.
Explained in Defense (Industries).