These diagrams are only available if you are using the SysML profile for your project. Parametric diagrams have the following general uses:
Parametric Diagrams cannot exist in isolation. They are created using model elements called constraint blocks that define generic or basic mathematical formulas.
To illustrate another possible use for a parametric diagram, a set of constraint blocks could define the volume of a tube, a disc, and the formula for an objects mass (Volume*Density). The parametric diagram would show how these constraint blocks combine, in a particular usage as a set of constraint properties, to give the mass of, perhaps, a tin can or a hollow cylindrical container based upon a set of input parameters. Constraint blocks are created within a block definition diagram, as described in Creating block definition diagrams.