SQL> create tablespace test datafile '/s01/orabase/oradata/mes/test01.dbf' size 5m autoextend off;

Tablespace created.

SQL> select * from dba_free_space where tablespace_name='TEST';

TABLESPACE_NAME                   FILE_ID   BLOCK_ID      BYTES     BLOCKS RELATIVE_FNO

------------------------------ ---------- ---------- ---------- ---------- ------------

TEST                                    5        128    4194304        512            5

SQL> 

SQL> select 4194304/1024/1024 from dual;

4194304/1024/1024

-----------------

                4

SQL> drop tablespace test including contents and datafiles;

Tablespace dropped.

SQL> 

SQL> create tablespace test datafile '/s01/orabase/oradata/mes/test01.dbf' size 20m autoextend off;

Tablespace created.

SQL> select * from dba_extents where tablespace_name='TEST';

no rows selected

SQL> select * from dba_free_space where tablespace_name='TEST';

TABLESPACE_NAME                   FILE_ID   BLOCK_ID      BYTES     BLOCKS RELATIVE_FNO

------------------------------ ---------- ---------- ---------- ---------- ------------

TEST                                    5        128   19922944       2432            5

SQL> select 19922944/1024/1024 from dual;

19922944/1024/1024

------------------

                19

SQL> drop tablespace test including contents and datafiles;

Tablespace dropped.

SQL> create tablespace test datafile '/s01/orabase/oradata/mes/test01.dbf' size 1g autoextend off;

Tablespace created.

SQL> select * from dba_free_space where tablespace_name='TEST';

TABLESPACE_NAME                   FILE_ID   BLOCK_ID      BYTES     BLOCKS RELATIVE_FNO

------------------------------ ---------- ---------- ---------- ---------- ------------

TEST                                    5        128 1072693248     130944            5

SQL> select 1072693248/1024/1024 from dual;

1072693248/1024/1024

--------------------

                1023