A transformation is a repository object that generates, modifies, or passes data. You configure logic in a transformation that the Integration Service uses to transform data. The Designer provides a set of transformations that perform specific functions. For example, an Aggregator transformation performs calculations on groups of data.
You can create transformations to use once in a mapping, or you can create reusable transformations to use in multiple mappings. When you add a reusable transformation to a mapping, you add an instance of the transformation. When you edit the reusable transformation in the Transformation Developer, all instances of the transformation in mappings inherit the changes. Some changes might invalidate the mappings using the reusable transformation.