oracle tablespace fragment question

 our customer said use that  sql check  tablespace  fragment   (db is oracle 10g)

select  tablespace_name,sqrt(max(blocks)/sum(blocks))*(100/SQRT(SQRT(COUNT(BLOCKS)))) fsfi   from dba_free_space  group by tablespace_name  order by 1;

 

-- they said FSFI(Free Space Fragmentation  Index ) value =100 ,means no tablespace fragment, the smaller the value,the much bigger

 Space Fragmentation  .

so they haver several question .

1.how to check tablespace  fragment  ,which sql.?

2.in 10g ,does tablespace fragment will effect the db performance ,does it critical ,how they effect db performance ?

3.what action can use to  resolve  the tablespace  fragment  ?

4.can we use