You can delete either all member mappings or only those mappings for which there is a tab in which mappings have been added
To delete member mapping from a selected tab:
From Data Load Mapping, select the tab from which to delete mappings.
For example, select the Explicit tab to view explicit type mappings.
To view all mappings, select the All Mappings tab.
Select the mapping and click Delete Mappings.
To delete multiple mappings, use the Shift key to select multiple mappings.
To delete all mappings, use Ctl + A key.
In Are you sure you want to delete the selected data load mapping(s), click OK.