Glossary
MAPPING1.MAP, MAPPING2.MAP, MAPPING3.MAP
The WMI repository's page maps: they translate logical page numbers of OBJECTS.DATA and INDEX.BTR into physical pages. Three generations are kept.
The MAPPING files translate the logical page numbers used by INDEX.BTR into physical pages of OBJECTS.DATA and of the index itself. Each file starts with the signature 0xABCD and holds two maps, one per file.
Windows keeps three generations to survive a failed write; the one with the highest version is current. A physical page that the current map does not reference is free — and may still hold deleted objects. See Inside OBJECTS.DATA.