Is it normal when I want to engineering some new entities from Logical to Relational that DM destroy my old design?
See the two images. I add only one new relation between two entities and I need to replace all my relational objects.
After selecting "Engineer to Relational Model" you are presented with the dialog box seen below.
On the "General Options" tab there is an option to "Engineer Coordinates".
When this is selected, your relational model diagram will be laid out similarly to your logical model diagram.
Uncheck it if you would like your relational model diagram to remain in tact as much as possible.
Hope this helps