truncate table后,FSFI值反而降低

数据库中有一个巨型表,有800多万张图片,占用空间一个多T
每天都进行大量的插入 删除
这几天插入图片速度明显下降,查看FSFI值如下column   FSFI   format   999,99   
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;   
spool   fsfi.rep;   
spool   off;  TABLESPACE_NAME                   FSFI
------------------------------ -------
CWMLITE                             56
DD                                1,00
DRSYS                             1,00
EXAMPLE                           1,00
INDX                              1,00
LICHENG                              4
SYSTEM                            1,00
TOOLS                             1,00
UNDOTBS                             23
USERS                             1,00truncate table后,再次查看FSFI如下
TABLESPACE_NAME                   FSFI
------------------------------ -------
CWMLITE                             56
DD                                1,00
DRSYS                             1,00
EXAMPLE                           1,00
INDX                              1,00
LICHENG                              1
SYSTEM                            1,00
TOOLS                             1,00
UNDOTBS                             22
USERS                             1,00我的TPXX表位于LICHENG表空间下
truncate table后licheng的FSFI值有4降为1
不是truncate可以清除碎片吗,怎么执行后不升反降了呢