several or one datafile makes  a tablespace.
when records are written to table , in the background, oracle looks for which tablespace is assinged and writes to any available datafile that the tablespace has.
thus table and tablespace are logical.
Datafile is physical.
there is no way to see, which table's record is in which datafile~!.
all u can map is tables and their tablespaces only.
Internally oracle maintains lotsa integrity.
so you cannot plug and play with a single datafile.
But if have transportable tablespaces defined,
then u can unplug it ( from the source) and plug it in(destination).