ORA-01555 caused by SQL statement

hi we have a 10g (10.1.0.2.0) db running on windows.user executed a qry to retrive the data from a table as of friday.

SELECT * FROM table1 AS OF TIMESTAMP TO_TIMESTAMP('2007-11-30 10:00:12', 'YYYY-MM-DD HH24:MI:SS') where tno='0104'

However he is getting snapshot too old error.. Actually we have shutdown the database on saturday for backup at 11.00am and again started at 16.00pm. We are able to see the data after 16.00pm(saturday.)

undo_retention=900
db_flashback_retention_target 1440
can any one tell us why we are not able to see friday's data.

If you get ORA-01555 error that should explain you the stuff. This means your undo retention time is small which is causing the issue.