BAPI_MATERIAL_SAVEDATA PERFORMANCE ISSUE

I want to create material by BAPI_MATERIAL_SAVEDATA.

I have about 60 thousand meterials should be upload to the system.But it is very slow(1 material more than one second ) when i use the bapi BAPI_MATERIAL_SAVEDATA,I use SE30 to check the time and found that FM GET_STPO_IDNRK takes a lot time,I dont know why it will check stpo when I create a material.(table STPO has more than 2million records)

Please help me to resolve this issue performance..

Thanks in advance.