then wouldn't it fail on this? this runs okay. that's what baffles me.

SQL>
SQL> select basename(file_name) baseXname from dba_data_files;

BASEXNAME
--------------------------------------------------------------------------------
system01.dbf
undotbs01.dbf
example01.dbf
indx01.dbf
tools01.dbf
users01.dbf
...
ABB0010D_dm01.dbf
ABB0010D_dm_idx01.dbf
ABB0010E_dm01.dbf
ABB0010E_dm_idx01.dbf

319 rows selected.