1.3.2.1.3 Initial Free Map (FMap) and Free Page Map (FPMap)
Article
Free Maps (FMaps) and Free Page Maps (FPMaps) are used to
search for contiguous free space within a PST file.<1> FMaps and
FPMaps are further described in greater detail in sections section 1.3.2.7
and section 1.3.2.8.