The Integration Service holds two different values for a mapping variable during a session run:
Start value of a mapping variable
Current value of a mapping variable
The current value of a mapping variable changes as the session progresses. To use the current value of a mapping variable within the mapping or in another transformation, create the following expression with the SETVARIABLE function:
SETVARIABLE($$MAPVAR,NULL)
At the end of a successful session, the Integration Service saves the final current value of a mapping variable to the repository.