Oracle Database Discussions

My question are
- how come the oldest_flashback_scn is 0
- how come oldest_flashback_time is empty

And I can still do "as of" query


SQL> select * from v$version;

BANNER
----------------------------------------------------------------
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Prod
PL/SQL Release 10.2.0.1.0 - Production
CORE 10.2.0.1.0 Production
TNS for 32-bit Windows: Version 10.2.0.1.0 - Production
NLSRTL Version 10.2.0.1.0 - Production


SQL> select
2 OLDEST_FLASHBACK_SCN,
3 to_char(oldest_flashback_time,'Dy DD-Mon-YYYY HH24:MI:SS'),
4 RETENTION_TARGET,
5 FLASHBACK_SIZE,
6 ESTIMATED_FLASHBACK_SIZE
7 from v$flashback_database_log;

OLDEST_FLASHBACK_SCN TO_CHAR(OLDEST_FLASHBACK RETENTION_TARGET FLASHBACK_SIZE ESTIMATED_FLASHBACK_SIZE
-------------------- ------------------------ ---------------- -------------- ------------------------
0 15 151461888 67700736

SQL>
SQL> select count(*) from test1 as of scn 364263;

COUNT(*)
----------
2097152