SQL> select file_id,tablespace_name,file_name,bytes/(1024*1024) as MB from dba_data_files where tablespace_name like 'TEST_T%';
FILE_ID TABLESPACE_NAME FILE_NAME MB
---------- --------------- ---------------------------------------- ----------
b.dbf
SQL> alter database datafile '/home/oracle/oracle/oradata/mdsp/test_tab.dbf' resize 21 m;
Database altered.
SQL> select file_id,tablespace_name,file_name,bytes/(1024*1024) as MB from dba_data_files where tablespace_name like 'TEST_T%';
FILE_ID TABLESPACE_NAME FILE_NAME MB
---------- --------------- ---------------------------------------- ----------
7 TEST_TAB /home/oracle/oracle/oradata/mdsp/test_ta 21
b.dbf
SQL> alter tablespace test_tab add datafile '/home/oracle/oracle/oradata/mdsp/test_tab1.dbf' size 20 m;
Tablespace altered.
SQL> select file_id,tablespace_name,file_name,bytes/(1024*1024) as MB from dba_data_files where tablespace_name like 'TEST_T%';
FILE_ID TABLESPACE_NAME FILE_NAME MB
---------- --------------- ---------------------------------------- ----------
7 TEST_TAB /home/oracle/oracle/oradata/mdsp/test_ta 21
b.dbf
8 TEST_TAB /home/oracle/oracle/oradata/mdsp/test_ta 20