Hi Zhang,
please go through thw below threads, hope you will get clarity.
http://help.sap.com/saphelp_erp60_sp/helpdata/en/aa/54f116da67444cba9da53a3fc1cf77/content.htm
https://scn.sap.com/thread/1356939
http://scn.sap.com/thread/1612271
Note : please search in google already related threads are available.
Regards
Dileep