"data dictionary indicates missing data file from system tablespace"
*Cause: Either the database has been recovered to a point in time in the
future of the control file or a datafile from the system tablespace was
omitted from the create control file command previously issued.
*Action: For the former problem you need to recover the database from a
more recent control file. For the latter problem, simply recreate the
control file checking to be sure that you include all the datafiles in
the system tablespace.