$ sqlplus / as sysdba 

 SQL> select instance_name from v$instance; 

 SQL> show user 

 export NLS_DATE_FORMAT='YYYY-MM-DD HH24:MI:SS'

 SQL> alter user scott identified by oracle account unlock; 

 SQL> grant execute on dbms_flashback to scott; 

 sqlplus scott/oracle 

 SQL> select systimestamp from dual; 

 SQL> select dbms_flashback.get_system_change_number() from dual; 

 SQL> create table emp2 as select * from emp; 

 SQL> select count(*) from emp2; 

 SQL> delete from emp2; 

 SQL> select count(*) from emp2; 

 SQL> select count(*) from emp2 as of scn <scn_number>; 

 SQL> insert into emp2 select * from emp2 as of scn <scn_number>; 

 SQL> select systimestamp from dual; 

 SQL> select count(1) from emp2; 

 SQL> delete from emp2 where deptno=30; 

 SQL> commit; 

 SQL> select systimestamp from dual; 

 SQL> select count(*) from emp2; 

 SQL> select count(*) from emp2 
as of timestamp(to_timestamp('2015-06-20 16:42:00','YYYY-MM-DD HH24:MI:SS')); 

 SQL> select count(*) from emp2 
as of timestamp(to_timestamp('2015-06-20 16:42:00','YYYY-MM-DD HH24:MI:SS')) where deptno=30; 

 SQL> insert into emp2 as select * from emp2 
as of timestamp(to_timestamp('2015-06-20 16:42:00','YYYY-MM-DD HH24:MI:SS')) where deptno=30;