Since the majority of geoprocessing tools take datasets as input and produce new datasets as outputs, most tool dialog boxes ask you where you want to write the output dataset. However, some tool dialog boxes will not ask you where to write output. The two primary reasons for this are the following:
- Though most geoprocessing tools produce new outputs datasets, some tools, such as Calculate Value or Get Count, write their result as a message or output value, while others, such as Spatial Autocorrelation, write HTML summaries. You can find these outputs in Geoprocessing History.
- Other tools modify their input dataset. For example, Add Field adds a new attribute field to the input dataset and doesn't require an output dataset. Several tools in the Editing toolbox modify the feature geometry of the input dataset.
If you are unsure if you want to modify the input dataset, you can do the following:
- Make a backup copy of the input features, then run the tool using one copy as input, leaving the other copy in its original state.
- A number of geoprocessing tools that modify the input dataset have an option to Start Editing so that the changes the tool makes to the input dataset can be undone.
- When input data is stored in a versioned geodatabase, tools will only modify the single version of the data. To apply changes to the rest of the database, the version must be reconciled and posted.