internal DOF

Hi All,

I am running a case with element number of 0.18M, and number of degrees of freedom solved is 311413 (plus 200428 internal DOFs). What is the internal DOF?

And I select the fully coupled solver. I find that COMSOL is running extremely slow. I don't know if the slow calculation speed is related to the internal DOF.

Is there any way to disable the intermal DOF?