A reference, which is typically located in response data, points to a specific value that you want to use in a subsequent test location, typically a request. You can substitute a request value with a reference. This substitution is called data correlation. You can also use a reference as input to an IF-THEN condition in a test or as input to custom Java™ code that your test calls.
A field reference points to an entire block of test data. For example, an entire HTTP response can be designated as a field reference. You can use a field reference as input to custom Java code that your test calls.
A reference that is created to be used by the HTTP secondary request cannot be used by custom code or other data sources.
If you select the Always log details checkbox, the details will be logged irrespective of the logging level set for a schedule. You must use this option only for debugging purpose.
You can always log the details of Substituters, Data Sources, and Requests.