During a message run, you can use mapping variables to temporary store values. You can write (calculated) values to a mapping variable, and later during the message run, read the value from the mapping variable. You can use mapping variables across records.
The mapping variable values are only stored during the message run. When the message run is finished, the mapping variable values are deleted.
During a message run, to read a mapping variable, on a field mapping, define the target field to be filled with the mapping variable value. Instead of a source field, use the 'Variable' field option to define the mapping variable which value must be used to set the target field value.

Standard procedure

1.	Click Connectivity studio Integration Design.
2.	On the Message tab, in the list, find and select the desired message.
3.	Click Edit.
4.	In the Mapping section, in the Target record pane, in the list, find and select the desired target record.
5.	On the Mapping tab, on the Field mapping tab, in the list, find and select the desired field mapping.
6.	Click the Field options tab.
7.	Select the Variable check box.
	Note: This check box is available only if a mapping variable is created for the message. If you have created a mapping variable, but the Variable field is not shown, refresh the page.
8.	Click the Variables tab.
9.	Define which mapping variable is used to set the target field value.
	In the Source variable field, enter or select a value.
10.	Close the page.