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AMD-00105:

Level "string" cannot be added to the hierarchy; the specified parent level "string" is already the parent of "string"
Cause: The level specified as the parent in the ADD_LEVEL_TO_HIERARCHY procedure could not be used, because it was the parent of another level within the hierarchy.
Action: In the ADD_LEVEL_TO_HIERARCHY procedure, specify a parent that is not already a parent of another level within a hierarchy.