does it create any problem if i change aggregation type of kyf in dso???

Dear experts,

  in my support project we are loading  2lis_02_scl data to 0pur_c01 .for stagging purpose there is a custom dso .for most of the datafeilds(for kyf alone ) aggregation type "summation " been used . because this when i rerun full infopackage(from setup table ) to bring back missed po docu ,these records adding to existing docu insted of overwritting .

can you please tell me why they have used summation property ??

if there is no specific purpose can you please tell me what are precations supposed to take before change aggregation type in transformations???

DSO :

key fileds                    data fields (with summation alone )

po doc no                    po order val

line item no                  po qty

sched line no               gr qty & val

schedul date                 ir qty & val

                                   no of schedule line in po

ex:

po doc no      lineitem no schedu line no schedule date po-val   po-qty gr qty ir qty

45001111          10            1                     10.01.2011     1000    10      0       0

45001111          10            1                     12.01.2011      0          0      5        5

45001111           10           1                      16.01.2011      0         0      3         0

45001111          10            1                     23.01.2011       0          0     2         5

thanks in advance

harry