Can Optistruct define a part to be rigid?

I know it can use RBE2 to let the part to be rigid.

 

But if today I want this component to be rigid.

 

Can I let the part to be rigid and not use the MPC method

 

I also have a question. My ram is 16GB and I use it to run, it will have the error.

 *** ERROR # 3401 ***
 System does not have enough memory available for MUMPS solver. MUMPS needs 
 addtional 64328 MB. Please use a computer with bigger physical RAM.

 

Can I use less ram to run? I set the-maxlen

 

and it also failed