> really makes me think that that area is just a comfortable way to
> access files on disk as memory areas; with the hope of propably better
> caching then not-memory-mapped files.
No, absolutely not. CreateFileMaping() does much the same thing
as mmap() in Unix.
> That would explain my disturbing impressions of performance of
> PostgreSQL on win32 rising when lowering shared_memory...
I don't know what your disturbing impressions are, but no it
doesn't explain them.