In some instances, when attempting to delete a field from an attribute table, the Delete Field option is disabled. Attempts to delete the field using the Delete Field tool return the following error message:
Error: ERROR 001334: Cannot delete required field <field>
This error occurs because the Field IsRequired (optional) option is checked when creating the field using the Add Field tool. Required fields are permanent by design and cannot be deleted.
As a workaround, export the attribute table using the Feature Class To Feature Class tool, and remove the desired field in the Field Map (optional) section. Complete the steps below to do so:
Note: Exporting the feature class to a geodatabase from the Catalog window also opens the Feature Class to Feature Class tool window. Using the Feature Class to Feature Class tool creates a new instance of the attribute table, and the required field in the original attribute table is not removed.