I think we have misunderstanding.

There is built in Schema in oracle in the name of HR and there is another shcmea which was created by me in the name of "TEST-12".
when ever that I use the DBMS_Stat for that schema , I get the error message as above. the problem is not the name , foeget the name,
if I create another schema in the name of XXX, still I have the same problem.
DBMS_Stat is working fine for some schema and doesn't for the one that I mentioned before.