Resize Datafile

In our production db, we have multiple data files for some tablespaces. Each file is around 40% used and having plenty of unused space. As such we are ending up so much of unused space for the entire tablespace. Below given is data for one such tablespace.

Tablespace                     File_name                                       Totalspace                         Freespace              Used space   Auto Extensible


PROD           E:\ORADB\ORADATA\GSCC\PRODGSCC01.DBF 20                                    17                          3                             YES

PROD          E:\ORADB\ORADATA\GSCC\PRODGSCC02.DBF   20                                   16                           4                             YES

PRODIX       E:\ORADB\ORADATA\GSCC\PRODIXGSCC02.DBF 20                                   18                           2                            YES

PRODIX       E:\ORADB\ORADATA\GSCC\PRODIXGSCC01.DBF 20                                   19                           1                            YES

We are planning to resize the data files so that the file size will be less and it would help reduce the time taken during cold backups