Oracle Database Express Edition (XE)

Hi,
I select a concatenation of rowid and ora_rowscn as

SQL>SELECT ROWID||ORA_ROWSCN FROM TT;

OUTPUT:
ROWID||ORA_ROWSCN
-----------------------------
AAADkOAAEAAAADWAAA1006305


Now when i select as 

SQL> SELECT * FROM TT
  2  WHERE
  3  ROWID = 'AAADkOAAEAAAADWAAA'
  4  AND
  5  ORA_ROWSCN = 1006305;

OUTPUT:
ONE
----------
A

but when i try to delete as

SQL> DELETE FROM TT
  2  WHERE
  3  ROWID = 'AAADkOAAEAAAADWAAA'
  4  AND
  5  ORA_ROWSCN = 1006305;

OUTPUT:
0 rows deleted.


Again, when i try Update as

SQL> UPDATE  TT SET ONE='PPP'
  2  WHERE
  3  ROWID = 'AAADkOAAEAAAADWAAA'
  4  AND
  5  ORA_ROWSCN = 1006305;

OUTPUT:
1 rows updated

Why this is so?

If it is BUG then, How can i raise a it for "Oracle Database 10g Express Edition" ?


Kind Regards,
Thanks.

Gurpreet S. Gill