Why am I getting "Error 000732, < dataset name > does not exist or is not supported", in a script run outside the ArcGIS environment?

Answer

In a geoprocessing model or script tool in a toolbox, users can refer to SDE data sources by a 'relative' path that contains the ArcCatalog connection name, such as:

'Database Connections/MyDatabaseName.sde/MyFeatureDatasetName/MyFeatureClassName'

The reference to 'Database Connections' is understood by ArcMap and ArcCatalog, but not by Windows. If a user runs a script having this type of connection string from a command line, scheduled task, Python development product, or other non-Esri environment, it is necessary to use the full Windows path to the connection file (.sde) on disk. A valid full path might look like this:

'C:/Users/<myusername>/AppData/Roaming/ESRI/Desktop10.3/ArcCatalog/Connection to mydb.sde'

By default, a connection file created in ArcCatalog is saved to the Windows user profile, but users can copy this file anywhere and reference it in any desired location. The Windows user profile is typically located in:

'C:/Users/<myusername>'