Call function in background

Hi everybody,

My issue is that I have create a module function which insert into database  .

loop AT t_DD02L into s_DD02L.


           CALL FUNCTION 'Z_GET_DURATION_QUERY' "in BACKGROUND TASK
             EXPORTING
               s_table       = s_DD02L-tabname
                     .

     ENDLOOP.

It doesn't insert if it's called in background and if it's called normally it works perfect!

help please,

thank you,

Sam ZA