A shapefile's FID and Shape field and a dBASE table's OID field can't be deleted. The OID field is a virtual column created by ArcGIS software when accessing the table's contents; it guarantees that each record in the table has at least one unique value. Shapefiles and dBASE tables must have at least one attribute field in addition to the FID and Shape fields or the OID field.
You can also delete fields with the Delete Field tool.
- In ArcCatalog, click the shapefile or dBASE table whose fields you want to delete.
- Click the File menu and click Properties.
- Click the Fields tab.
- Position the pointer over the gray button to the left of the column you want to delete.
The pointer's icon changes to an arrow.
- Click the gray button to select the column.
The field is selected and its properties appear in the Field Properties list.
- Press the DELETE key.
The selected field is removed from the list.
- Click OK.