Is there an option to keep scrollY always ON?

Mir

I want my table to be of fixed height with scrollY always ON and have 'No. of rows'='selected length' at any given point. As such I am adding empty filler rows to keep number of rows equal to the selected length in "fnDrawCallback" function. So far everything looks fine.

However the problems of header misalignment comes in when I paginate to the last page (having filler rows). When I removed the "fnDrawCallback" function, I could see the cause for this problem. Actually, as there will be few rows which does not fit the table view, it tries to remove the scroll & headers push to right end leaving no space for scrollY. Then when I add filler rows in fnDrawCallback, it adds the scrollY but does not push the header left with scrollbar numbr of pixels. Hence there is mis-alignement of header & data columns.

What could be the best way to acheive this?
OR
Is there an option to keep the scrollY always enabled regardless of number of rows in table.