Dear, All
 
What is DEFPLOT, I try to modify but not allowed.
 
please advise.

Are you referring to the "defpoints" layer?

yup, i referring to defpoints layer.

When you create a Dimension, a "defpoints" layer is automatically created.  It contains the DEFinition POINTS of the dimensions.  If you delete all dimensions, you should be able todelete the layer with the "purge" command.