In eDirectory, indexes are created automatically when an attribute has more than 25 values or if the value of the attribute is more than 2048 bytes. Such attributes are moved to a separate attribute container and indexes are created for them. These auto-generated indexes are marked as system indexes. eDirectory does not permit deleting system indexes and hence, any attempt to delete them gives an error.
To workaround this issue, add the following value in the in _ndsdb.ini file in the DIB directory, and then restart ndsd:
This prevents the attributes from being moved to the attribute container. However, this command will not affect the attributes that are already there in the container.