issue in smp 2.3

hi,

I am facing a problem while using webservice for mbo. the problem is that in my webservice the input field is a Array of Ids . When i use it my code in smp 2.3 it create a list in that one more list .

I solve this also but now problem is that i use policy "Om Demand "
Ehile synch it hits webservice two times first is with null and another is with data.

I fully checked with my code level . I called synchronise only one time with data.

But please tell why this issue occurs??

How can i resolve this issue?