ORA-22285 Error while trying to register an xsd schema on oracle database
Unless specified otherwise, directory objects names are stored as uppercase strings, and you need to reference them like that in such cases:

SQL&gt; !ls -l /home/oracle/hello.txt
-rw-r--r--. 1 oracle oinstall 6 Jan  9 14:05 /home/oracle/hello.txt

SQL&gt; create or replace directory hello as '/home/oracle';

Directory created.

declare
  v_file bfile;
  ret integer;
begin
  v_file := bfilename('hello', 'hello.txt');
  ret := dbms_lob.fileexists(v_file);
end;
  8  /
declare
*
ERROR at line 1:
ORA-22285: non-existent directory or file for FILEEXISTS operation
ORA-06512: at "SYS.DBMS_LOB", line 803
ORA-06512: at line 6


declare
  v_file bfile;
  ret integer;
begin
  v_file := bfilename('HELLO', 'hello.txt');
  ret := dbms_lob.fileexists(v_file);
end;
  8  /

PL/SQL procedure successfully completed.

SQL&gt;