When you use OPEN_FORM or CALL_FORM to create a multiple-form application, usually you should avoid defining a root window in any of the form modules that you plan to display at the same time. At runtime, only one root window can be displayed at a time, even in a multiple-form application. This means that if the first canvas displayed by Form B is a content view assigned to the root window, it will display in the root window of Form A, not in a separate root window of its own. As a result, Form B's content canvas will hide any Form A canvases already displayed in the root window. For most multiple-form applications, this is not the desired behavior.
If you must use a root window, you can prevent the second form from hiding the first. Make sure that the target canvas (displayed by the second form) is one of the following:
When the target canvas is assigned to a different window, Oracle Forms displays the second form in a separate window, and the first form's root window display remains unchanged.
When the target canvas is a stacked canvas assigned to the root window, Oracle Forms displays it in the first form's root window. However, if the stacked canvas is smaller than the content canvas (usually the case), the first form's content canvas remains at least partially visible.