Rules for using tools within an edit session
If you are editing data in ArcMap, and you use a geoprocessing tool that either
- uses a layer that is being edited as input or
- creates data in the same workspace as the layer being edited,
the tool may return an error because it cannot modify the input data for the reasons described below.
First, a couple of definitions you need to know are presented here:
- Edit session: When you are editing data in ArcMap, you are said to be in an edit session.
- Edit workspace: This is the workspace containing the data currently being edited.
Overwriting existing data in the edit workspace
If you are in an edit session, existing data in the edit workspace cannot be overwritten by a tool, even if the geoprocessing options have been set to Overwrite the outputs of geoprocessing operations. Tools will stop execution and return an error.
Creating new data in the edit workspace
When the result of a tool is written to the edit workspace, these results are considered part of the edit session. To preserve the tool's results, you must save your edits.
Creating new shapefiles
Shapefiles created in the edit workspace cannot be edited. You must first save your edits and end the edit session, then start a new edit session.
Normally, when you end an edit session, you are asked if you want to save your edits. When creating a new shapefile in the edit workspace, you will not be prompted to save your edits unless you've performed other edits on existing shapefiles in the edit workspace. Therefore, it's important that you first save your edits, then end the edit session.
Updating existing data
When editing a feature class or table, you are not allowed to make schema changes. A schema change is a change to the fields, such as adding a new field (Add Field) or deleting existing fields (Delete Field). Tools that alter schemas will return an error message if the input is being edited.