drop table t;

create table t
nologging
compress
pctfree 0
as
select 'ABCDEFGHIJKLMNOP' col1
from   dual
connect by level <= 10000
/
commit
/

select blocks
from   user_segments
where  segment_name = 'T' and
       segment_type = 'TABLE'
/

update t
set    col1 = col1
/
commit
/

select blocks
from   user_segments
where  segment_name = 'T' and
       segment_type = 'TABLE'
/