create table odrm_del
as  select *
from odrm
as of timestamp to_timestamp（'2011-04-27 12:00:00', 'yyyy-mm-dd hh24:mi:ss')

------解决方案--------------------
有备份否？ 如果有备份的话，
先restore database;

recover database until time "to_date('','')";
alter database open;