There will be decreasing performance of oracle by delete who

There will be decreasing performance of oracle by delete whole table and then insert ...

There is a project that need collecting periodically  (2 months) data into one table and then exporting it  as excel file. The table is a temporary table, the app do that 

delete from tb_name;

insert into tb_name values.....
...
insert into tb_name values.....

With that method, it would be causing more and more tablespace fragments, and make the performance decresing.

In other to avoid this disadvantage influences, I suggest programer modify the app as 

truncate table tb_name drop storage;

insert into tb_name select * from ...

The delete operation will be causing tablespace fragments.