What is a dynamic layer?

Dynamic layers are composed of one or more sub-layers that display some geographic phenomena in a map image. They are connected to a non-cached map service that generates map images on the fly. Though these images themselves do not contain any information about the features in the map, the underlying data is accessible from a client application, for example by querying the layer or doing an identify operation. Dynamic layers are automatically re-projected to the map's spatial reference, so no additional work is required for the dynamic layer to align correctly with a basemap that was added to the map before the dynamic layer.

Dynamic layers allow the execution of various ArcGIS Server requests from a client application. The client side requests that can be issued to ArcGIS Server include the ability to:

Dynamic layers are commonly used as operational layers and can be used as a basemap layer if no tiled map service layer is being used. A dynamic layer is often used in conjunction with a feature layer in selection mode to show the latest map data without having to pull all of the feature information from the server (as with feature layers) on every map request.