init file or spfile

[dbasan]

You can type in sqlplus:

show parameter spfile

If its set it would give you the path else "unknown show option" error, similarly try with pfile.

I got this when i googled, give a try next time

select decode(count(*), 1, 'spfile', 'pfile' ) from v$spparameter where rownum=1 and isspecified='TRUE';
-courtesy TomKyte

This would be usefull for all who needs.