Hi Dieter,
Please check also these 2 important notes about the subject:
1622837 - Secure connection of AS ABAP to Oracle via SSFS
1639578 - SSFS as password storage for primary database connect
For the error "ORA-01017: invalid username/password; logon denied" , update those user(s)' passwords with that command. Connect to your db as admin:
1-oraSID: sqlplus / as sysdba
2-SQL> alter user <USERNAME> identified by <PASSWORD> account unlock;
Then try the password whether it works or not:
3-oraSID: sqlplus <USERNAME>/<PASSWORD>
Regards,
Serhat