You can specify which map service is used for the overmap in its config file. If no layer is specified in the config then the overview map will use the basemap service currently selected.
So if you want to show your basemap with operational layers over the top you will need to create a combined service that you then specify in the config file, see:
thanks for your answer , What I understanding from you and helping Esri ,
I copy url (my service) on the config overviewMap by format xml , as you see in the below .. it is right or not ??
<?xml version="1.0"?> <configuration> <!-- possible values for initialstate: open or closed (default) --> <initialstate>closed</initialstate> <!-- by default it will use the same basemap as current main map, you can hardcode as below if you wish --> <!-- <layer type="tiled" url="http://my server/arcgis/rest/services//GeneralServices/General_Services/MapServer?f=jsapi"/> --> </configuration>