SQL & PL/SQL

I can not see a view or tables in remote a_database, I only may select from a_view

1.
SELECT a_date
  FROM a_view@a_database

2.         
SELECT TO_CHAR (a_date, 'mm/dd/yy')
  FROM a_view@a_databse


---

[pre]
3.
SELECT *
  FROM a_view@a_database
 WHERE TO_CHAR (a_date, 'mm/dd/yy') = TO_CHAR (SYSDATE, 'mm/dd/yy')

[pre]
4.
SELECT MAX (a_date)
  FROM a_view@a_database

--

Select 1 and 2 are OK
Select 3 and 4 give me an error
ORA-01843: not a valid month
ORA-02063: preceding line from A_DATABASE

Ignore this if more information needed.
I only need a possible version of a problem?

Edited by: Bolev on Sep 2, 2008 6:49 PM