SELECT * FROM v$pwfile_users WHERE sysdba='TRUE'

and it return error as below

ERROR:
ORA-00600: internal error code, arguments: [KSSRMP1], [], [], [], [], [], [], []

also
connect / as sysdba
grand sysdba to user username
error show beloww

ORA-01994: GRANT failed: cannot add users to public password file

but password file has been created long time ago by previous DBA.

Thanks,