LoadRunner can detect dynamic values in the script and suggest their replacement with parameters. For automatic correlation, LoadRunner uses rule-based, recording-based, and replay-based correlations.
LoadRunner comes with a set of predefined, extendable rules for how to correlate dynamic values in well-known environments.
Example: An example of a rule in pseudo-code might be:
Find text in the response headers between "Timeout: " and the next white space and save it in parameter "Timeout".
During code generation, LoadRunner scans server responses for values that match the Correlation Rules. When a matching value is found, LoadRunner adds a step to extract the value and save it in a parameter.
Then, the script code is scanned for the value and matches are replaced with a reference to the parameter.
For information about tuning the rules-based correlation, see Automatic Correlation Configuration.
After code generation, the script is scanned for additional correlation candidates in the client request steps. If a candidate was received from the server before it is sent by the client, it is suggested as a correlation. The suggestion includes the exact description of where and how to extract the dynamic value from the server response and where to replace data with a parameter.
You can accept suggestions in the Design Studio.
Replay the script at least once. It is not a problem at this stage if some steps fail.
The Replay-based scan compares the server responses before the failures for mismatched values. If such mismatched values are used in the script, they are suggested as correlations.
Repeat this process until the last failure is detected and correlated.