Save Change Script Dialog Box
Displays a change script whenever you save a table or diagram while there are unsaved database changes in it. The dialog box lets you save the change script as a text file with an .sql extension.
This dialog box appears when you choose Save Change Script from the File menu or click the Save Change Script button 
on the Database Designer toolbar.
Yes
Displays the Save As dialog box, prompting you for a destination file to contain the change script.
No
Cancels the save action.
Automatically generate change script on every save
Select this option to create a change script each time you save the database diagram or selected tables. This provides a record of all changes made to the database.
If you have selected to have a change script created automatically each time you save, this dialog box will not appear when you save your database diagram.
For more information about saving SQL change scripts, see Saving a Change Script.