If a topology contains many smaller polygons, you can create a new topology by combining polygons that share the same data value in a specified field. This field is called the dissolve field. The dissolve field can be an object data field or a column in a linked external database.
When you dissolve a topology, AutoCAD Map 3D checks each boundary between polygons to see if the dissolve field value is the same for both. If so, the boundary and one of the centroids are removed. All object fields except for the dissolve and any new topology fields are removed.
When you dissolve a network topology, AutoCAD Map 3D checks nodes between lines to see whether two lines intersect at a specified node and whether the dissolve field is the same. If so, the node is removed, and the two links are joined to form one link. All object fields except for the dissolve and any new topology fields are removed as shown in the following illustration.