Certain applications use dynamic parameters to manage sessions.
The parameter is created by the server and it changes each time the scenario is run. To be able to simulate this behavior perfectly, the dynamic parameter returned by the server needs to be extracted (usually within a hidden form field or a link) and replaced in the following requests.
The extraction is done using a variable extractor. Select the request, click on the Advanced button, then select Variable extractor.
For more information about defining variable extractors, see Advanced parameters.
For more information, see Create a variable extractor.