SQL> alter system flush buffer_cache;

System altered.

SQL> create table t ( x primary key, y ) as select 1 x, 2 y from dual;

Table created.

SQL> select data_object_id from user_objects where object_name = 'T';

DATA_OBJECT_ID
--------------
        101919

SQL>
SQL> select
  2    dbms_rowid.rowid_relative_fno(rowid) f,
  3    dbms_rowid.rowid_block_number(rowid) b
  4  from t;

         F          B
---------- ----------
         7      16259

--
-- here's the freshly created block
--

SQL> select status
  2  from   v$bh
  3  where  file# = 7
  4  and    block# =  16259
  5  and    objd = 101919
  6  /

STATUS
----------
xcur

--
-- if I flush the buffer cache, the block is still "there" but its marked as free, ie, I could replace it
-- with something else
--
SQL> alter system flush buffer_cache;

System altered.

SQL> select status
  2  from   v$bh
  3  where  file# = 7
  4  and    block# =  16259
  5  and    objd = 101919
  6  /

STATUS
----------
free

--
-- I query it back in, and it is the current version of this block because
-- nothing else has ever need to read it consistently
--
SQL> select * from t where x=1;

         X          Y
---------- ----------
         1          2

SQL> select objd, status
  2  from   v$bh
  3  where  file# = 7
  4  and    block# =  16259
  5  and    objd = 101919
  6  /

      OBJD STATUS
---------- ----------
    101919 xcur

--
-- now I delete it (without commit)
--
SQL> delete from t;

SQL> select objd, status, dirty
  2  from   v$bh
  3  where  file# = 7
  4  and    block# =  16259
  5  and    objd = 101919
  6  /

      OBJD STATUS     DIRTY
---------- ---------- -----
    101919 xcur           Y

--
-- and now another session gets an older version of it via a query
--
SQL> select * from t where x=1;

         X          Y
---------- ----------
         1          2

--
-- and we can see the consistent version be created
--

SQL> select objd, status
  2  from   v$bh
  3  where  file# = 7
  4  and    block# =  16259
  5  and    objd = 101919
  6  /

      OBJD STATUS
---------- ----------
    101919 xcur
    101919 cr