gap in v$session

Hi all,

on 9i, my database started on June 30. When I query V$SESSION I have a gap for logon_time between 30/06/2014 03:52:29  and 01/07/2014 20:41:39 :

select to_char(startup_time,'DD-MON-RR HH:MI AM') from v$instance;

TO_CHAR(STARTUP_TI

------------------

30-JUN-14 03:52 AM

1 row selected.

select logon_time from v$session order by logon_time desc--where logon_time > sysdate-1

TO_CHAR(LOGON_TIME

------------------

01-JUL-14 08:41 PM

01-JUL-14 08:41 PM

01-JUL-14 08:41 PM

30-JUN-14 03:52 AM

How to explain that ?

Are the session historicized in any table (in 9i)

Thank you.