set line 300
col file_name format a50
select file_name, AUTOEXTENSIBLE,  MAXBYTES /1024/1024/1024 mxsz , BYTES/1024/1024/1024 sz
from dba_data_files where TABLESPACE_NAME='UNDOTBS1';

alter database datafile '/u01/app/oracle/oradata/discover/users02.dbf' autoextend on maxsize 31G;