SQL & PL/SQL :: Difference In Table Data Between Sessions

I create table in session1:

create table marco_tmp_270511
as
select 5 as t from dual

Then I log in session2 and perform query to

select * from marco_tmp_270511 and receive 5 in column t.

Then I return to session1 and perform:

delete marco_tmp_270511;
insert into marco_tmp_270511
select 99 as t from dual ;
select * from marco_tmp_270511;

Then I go again to session2 and perform query to

select * from marco_tmp_270511

and still receive 5 in column t. How do I synchronize data between sessions?