No Able to change Structure.

Hello Guys,

I am getting an error while trying to change my structure by SE11(Not able to go to change mode).The error is " DDIC change restriction to prevent DB inconsistencies".(Also attached screenshot for the error).The Structure is of of Activation type 00 and Enhancement category "Cannot be enhanced".
I already tried commenting the program and an RFC which were using the structure.Please Suggest.