file_io script in oracle 10g

SET PAGESIZE 1000

SELECT Substr(d.name,1,50) "File Name",
       f.phyblkrd "Blocks Read",
       f.phyblkwrt "Blocks Writen",
       f.phyblkrd + f.phyblkwrt "Total I/O"
FROM   v$filestat f,
       v$datafile d
WHERE  d.file# = f.file#
ORDER BY f.phyblkrd + f.phyblkwrt DESC;

SET PAGESIZE 18