Increasing tablespace size, Oracle

Checking sizes:
SELECT * FROM DBA_DATA_FILES;

Resizing:
ALTER DATABASE DATAFILE ‘D:\ORACLEXE\ORADATA\XE\USERS.DBF‘ RESIZE 200M;

Addind Datafile to existing Tablespace:
ALTER TABLESPACE USERS ADD DATAFILE ‘D:\ORACLEXE\ORADATA\XE\USERS_2.DBF‘ SIZE 50M;