How to know how much I can shrink the table

Question

How can I know how much I can shrink the table after firing the delete statement?

Answer 1

Hi,
alter table table_name shrink space;
For example:
create table HWM_TEST(
  ID      NUMBER,
  DB_USERVARCHAR2(12),
  TARIH   DATE
  STORAGE(
          MAXEXTENTS       UNLIMITED
insert into HWM_TEST
  select level   id,
          user    db_user,
          sysdate tarih
   from dual
  connect by level<100001;
  commit;
  100000
rows created.
  Commit complete.
  insert into HWM_TEST
  select * from HWM_TEST;
  insert into HWM_TEST
  select * from HWM_TEST;
  insert into HWM_TEST
  select * from HWM_TEST;
  insert into HWM_TEST
  select * from HWM_TEST;
  insert into HWM_TEST
  select * fromHWM_TEST;
  commit;
  100000
rows created.
  200000
rows created.
  400000
rows created.
  800000
rows created.
  1600000 rows created.
  Commit complete.
select count(*) from hwm_test;
   COUNT(*)
3200000
   1 row selected.
  Elapsed: 00:00:02.26
delete from HWM_TEST;
  commit;
  COUNT(*)
0
  1 row selected.
  Elapsed: 00:00:02.42
  alter table HWM_TEST enable row movement;
  alter table HWM_TEST shrink space;
  set timing on
  select count(*) from hwm_test;
COUNT(*)
0
   1 row selected.
  Elapsed: 00:00:00.01
Thank you