what is a reusable transformation?

  Reusable transformation can be a single transformation.This transformation can be used in multiple mappings.when you need to incorporate this transformation into mapping you add an instance of it to mapping.Later if you change the definition of the transformation, all instances of it inherit the changes.Since the instance of reusable transformation is a pointer to that transformation.U can change the transformation in the transformation developer, its instance automatically reflect these changes. This feature can save U great deal of work.

-- what are the methods for creating reusable transformation?

      Two methods

1)      Design it in the transformation developer.

2)      Promote a standard transformation from the mapping designer.After you add a transformation to the mapping, you can promote it to status of reusable transformation.

Once you promote a standard transformation to reusable status, you can demote it to a standard transformation at any time.

If u change the properties of a reusable transformation in mapping , you can revert it to the original reusable transformation properties by clicking the revert.