You can create mapping parameters and variables in the Mapping Designer or Mapplet Designer. Once created, mapping parameters and variables appear on the Variables tab of the Expression Editor. Use them in any expression in the mapplet or mapping. The Designer validates mapping parameters and variables in the Expression Editor of mapplets and mappings.

Use mapping parameters and variables in a source qualifier in a mapplet or mapping. When you use mapping parameters and variables in a Source Qualifier transformation, the Designer expands them before passing the query to the source database for validation. This allows the source database to validate the query.

When you create a reusable transformation in the Transformation Developer, use any mapping parameter or variable. Since a reusable transformation is not contained within any mapplet or mapping, the Designer validates the usage of any mapping parameter or variable in the expressions of reusable transformation. When you use the reusable transformation in a mapplet or mapping, the Designer validates the expression again. If the parameter or variable is not defined in the mapplet or mapping, or if it is used incorrectly in the reusable transformation, the Designer logs an error when you validate the mapplet or mapping.

When the Designer validates a mapping variable in a reusable transformation, it treats the variable as an Integer datatype.

You cannot use mapping parameters and variables interchangeably between a mapplet and a mapping. Mapping parameters and variables declared for a mapping cannot be used within a mapplet. Similarly, you cannot use a mapping parameter or variable declared for a mapplet in a mapping.