Duplicate inputs are not allowed

Error Message

When utilizing a geoprocessing tool and specifying layers with identical names but differing sources as inputs or targets for the tool, a red X with the following error message is returned:

"Duplicate inputs are not allowed".

Cause

The geoprocessing tool validates layer inputs exclusively by their layer names. The tool treats both inputs as coming from the same source, and will not execute until one of the conflicting inputs has been removed.

Solution or Workaround

One of the layers with the same name needs to be modified for the geoprocessing tool to accept both layers. The layer name can be modified by selecting one of the following methods:

Option 1

1. Access the Layer Properties dialog box by either double-clicking the layer's name, or by right-clicking the layer and selecting Properties.
2. Select the General tab.
3. Modify the entry displayed in the Layer Name field.

Option 2

1. Select the layer name in ArcMap's Table of Contents.
2. Press the F2 key on the keyboard or click the layer name once more to edit its name.