Required for efficient N-glycosylation. Necessary for maintaining optimal levels of dolichol-linked oligosaccharides. Hydrolyzes dolichyl pyrophosphate at a very high rate and dolichyl monophosphate at a much lower rate. Does not act on phosphatidate (By similarity). a dolichyl diphosphate + H2O = a dolichyl phosphate + H(+) + phosphate Protein modification; protein glycosylation. Belongs to the dolichyldiphosphatase family.