According the init. parameter UNDO_RETENTION = 900 (15 min) you can see the tuples versions as below:
select * from
VERSIONS BETWEEN TIMESTAMP
to_timestamp('2011/06/07 9:30:00', 'YYYY/MM/DD HH24:MI:SS')
AND
to_timestamp('2011/06/07 9:35:00', 'YYYY/MM/DD HH24:MI:SS')
