create table t1(code number)tablespace test;
insert into t1(123);
commit;
alter system switch logfile;
alter database begin backup;
cp'/home/oracle/../test.dbf '/home/oracle/../backup/test.dbf
cp'/home/oracle/../system.dbf' '/home/oracle/../backup/system.dbf
.
.
.
cp '/home/oracle/../dtf1' '/home/oracle/../backup/dtf1.dbf
alter database end backup;
select *from current_timestamp from dual;(30-dec-2011:11:00:00)
insert into t1(456);
commit;
alter system switch logfile;
shutdown immediate;
rm'/home/oracle/../test.dbf'
rm'/home/oracle/../system.dbf'.
.
rm '/home/oracle/../users.dbf' 

mv'/home/oracle/../backup/test.dbf''/home/oracle/../test.dbf'
mv'/home/oracle/../backup/system.dbf''/home/oracle/../system.dbf'
.
mv'/home/oracle/../backup/users.dbf' '/home/oracle/../users.dbf' 
startup mount;
recover database until time '30-dec-2011:11:00:00';
alter database open resetlogs;