Several tools including Calculate Field, Integrate, Append, Snap, Align Features, and others have a toggle button next to the Run button on the tool dialog to Enable Undo. If this option is toggled on, when you click Run, an edit session is started, tool processing is performed, and after completion the edit session remains open so you can undo the changes the tool made to the input data.
ArcGIS Pro automatically starts editing when you create or modify features or attributes, and there is no explicit way to start editing. The Enable Undo toggle button in the Geoprocessing pane is a shortcut to start and leave an edit session active, specifically for use with geoprocessing tools that modify the input data.
Geoprocessing tools that add or delete fields, or perform other schema changes, cannot be run in an edit session. Some tools that support Enable Undo may add a field and calculate values into the new field, such as Near. If you undo this tool, the field will not be removed from the data, but the contents of the field will be set to <Null>.
Undo and redo
After toggling on Enable Undo and running the tool, evaluate the results to determine if you want to keep the changes made to the input data. A banner is added near the top of the Geoprocessing pane to indicate the pending edits. To help you evaluate and visualize the changes made to the data, the banner includes controls to Undo and Redo the changes made by the tool.
Save or discard changes
If you decide to keep the changes to the data made by the tool, you must click Save Edits to commit the edits. If you do not want to keep the changes, click Discard Edits to revert changes made by the tool.
If you do not save or discard your edits, other geoprocessing tools will be run in the open edit session, which can have unintended implications on performance and application behaviors. See the Considerations section below for more information.
Saving or discarding the edits closes the edit session started by running the geoprocessing tool. After saving or discarding the edits, you can no longer undo or redo the operation.
When deciding to run geoprocessing tools with Enable Undo toggled on, the following should be considered.
When geoprocessing tools are run in an edit session, the tools are run in the main application thread. This means that the application will be blocked from other tasks while the tool is running.
Performance and scalability
When geoprocessing tools are run in an edit session, performance will decrease compared to when the same tool is run outside an edit session. Similarly, scalability will decrease, as fewer features can be processed in an edit session compared to outside an edit session.
Deleting or overwriting datasets
Geoprocessing tools that delete or overwrite datasets cannot be run in an edit session. You also cannot delete datasets from these locations in the Catalog pane using the right-click Delete command.