Mapping parameters and variables represent values in mappings and mapplets.
When we use a mapping parameter or variable in a mapping, first we declare the mapping parameter or variable for use in each mapplet or mapping. Then, we define a value for the mapping parameter or variable before we run the session.
A mapping parameter represents a constant value that we can define before running a session.
A mapping parameter: retains the same value throughout the entire session. Example: When we want to extract records of a particular month during ETL process, we will create a Mapping Parameter of data type and use it in query to compare it with the timestamp field in SQL override.
After we create a parameter, it appears in the Expression Editor. We can then use the parameter in any expression in the mapplet or mapping. We can also use parameters in a source qualifier filter, user-defined join, or extract override, and in the Expression Editor of reusable transformations. MAPPING VARIABLES:
Unlike mapping parameters, mapping variables are values that can change between sessions. The Integration Service saves the latest value of a mapping variable to the repository at the end of each successful session. We can override a saved value with the parameter file. We can also clear all saved values for the session in the Workflow Manager.