Hi,

This attribute serves to control the availability of the "Duplicate" option for a record within the form view.
example:

<record id="product_product_view_form" model="ir.ui.view">
<field name="name">product.product.view.form</field>
<field name="model">product.product</field>
            <field name="arch" type="xml">
                <form duplicate="0">
                    <group>
                        <!-- Field for Product Name -->
                        <field name="name"/>
                    </group>
                </form>
            </field>
        </record>

Hope it helps