error_code=64

That is a warning ! It means you are doing something wrong and it will come with an messege.

 This specific error is related to the fact that your hint/label identifier starts with numeric character which cannot.

- this happened to me in Microstrategy while setting labes using Reports GUIDs.

Here is shot demo of this warning in action:

- this warning msg you will get it at vsql command line. 

-- wrong label
dbadmin=> select /*+label(1label_name)*/ 4 from dual;
WARNING 3628:  Invalid character in hint at or near "(1" at character 16
 ?column?
----------
        4
(1 row)
-- good label
dbadmin=> select /*+label(label_name)*/ 4 from dual;
 ?column?
----------
        4
(1 row)

dbadmin=> SELECT session_id   FROM CURRENT_SESSION;
        session_id
--------------------------
 prodvert01-47446:0x189bb
(1 row)

dbadmin=> \x
Expanded display is on.
dbadmin=> select * from error_messages where session_id='prodvert01-47446:0x189bb';
-[ RECORD 1 ]---+------------------------------------------
event_timestamp | 2015-10-08 10:40:39.275538+11
node_name       | v_analytics_node0004
user_id         | 45035996273704962
user_name       | dbadmin
session_id      | prodvert01-47446:0x189bb
request_id      | 0
transaction_id  | 45035996307835116
statement_id    | -1
error_level     | WARNING
error_code      | 64  -- here is your error code
message         | Invalid character in hint at or near "(1"
detail          |
hint            |

- i hope this help, and there are some other posts where people state is a bug, is not.