Source determination

Hi Guys

I have a confusion, in regard to source determination.

There are two vendors for a material. I have maintained Quota Arrangement for that material to both the vendors. And also in the source list for that material I have included both the vendors.

My concern is during MRP run, schedule line is created for only one vendor. Can any one let me know why schedule line for other vendor was not created.

Regards

Prashant