Target mapping issue

Hi All , recently i created a custom target mapping on acc v8 lets say named as “ABC” out of which 3 schemas for delivery, exclusion, tracking where created but now i want to delete it as requirement changes , but while deleting its giving “delivery linked” error i too check that no delivery is linked as it is new instance , secondly tried renaming and tried to create new target mapping on same schema but not able to save it it giving error and finally not able to create any new target mapping on schema used un ABC while i can create target mapping with other schema , how to resolve it .