Creating a map topology

Steps:

1. Click the Map Topology button on the Topology toolbar.
2. Check the feature classes that will participate in the map topology. All the layers in your current edit session that can participate in the map topology are listed on the dialog box. Layers representing annotation and dimension feature classes and feature classes that participate in a geometric network cannot be included in a map topology and will not be listed.
Note:

You cannot edit layers that are projected on the fly using a map topology. To create a map topology, all the layers must have the same coordinate system, which must match the coordinate system of the data frame.

3. Optionally, set a cluster tolerance for the map topology. The default cluster tolerance is the minimum possible cluster tolerance. Increasing the cluster tolerance may cause more features to be snapped together and considered coincident, but this may reduce the spatial accuracy of your data.
4. Click OK.