Change the properties of a tablespace.
  
  Syntax:
ALTER TABLESPACE tablespace_name option
 options: 
The option used with this command can be any one of the following:
    ADD {TEMPFILE|DATAFILE} 'filespec' [AUTOEXTEND OFF] SIZE int {K|M}
    ADD {TEMPFILE|DATAFILE} 'filespec' SIZE int {K|M}
       [ AUTOEXTEND ON [NEXT int K | M] 
           [MAXSIZE {UNLIMITED|int K|int M}] ]
    RENAME DATAFILE 'filename' TO 'filename'
    {TEMPFILE|DATAFILE} ONLINE
    {TEMPFILE|DATAFILE} OFFLINE
    MINIMUM EXTENT int {K|M}
    COALESCE
    DEFAULT STORAGE storage_clause
    ONLINE
    OFFLINE {NORMAL | TEMPORARY | IMMEDIATE}
    {BEGIN | END} BACKUP
    READ {ONLY | WRITE}
    PERMANENT | TEMPORARY
    LOGGING | NOLOGGING
    [NO] FORCE LOGGING
Examples
Alter Tablespace TEMP ADD TEMPFILE 'T:\oradata\live\Temp02.DBF' SIZE 800M;
Alter Tablespace SS64 ADD DATAFILE 'T:\oradata\live\Data02.DBF' SIZE 1500M;
More examples - Morgans Library
 "God grant us the serenity to accept the things we cannot change, courage to change the things we can, and wisdom to know the difference." - Reinhold Niebuhr - The 12 step program 
  
Related Oracle Commands:
DBMS_SPACE_ADMIN
CREATE TABLESPACE 
DROP TABLESPACE
Related Views:
DBA_DATA_FILES DBA_TABLESPACES USER_TABLESPACES DBA_TEMP_FILES DBA_TS_QUOTAS USER_TS_QUOTAS