You can use the Patterns page of the Preferences window to control the initial visibility of the overview compartment in pattern instances on the diagram view. The overview graphic is usually a UML class diagram of the pattern and is included as part of the pattern.
The overview graphic also appears on the Overview pages of both the Pattern Explorer view and the Properties view. However, this preference only modifies how it appears in the pattern instance on the diagram view.
To set default preferences for the overview compartments in pattern instances on the diagram view: