Correlation

The purpose of Correlation is,

To simplify or optimize your code
For example, if you perform a series of dependent queries one after another, your code may become very long. To reduce the size of the code, you can nest the queries, but then you lose precision and the code becomes complex and difficult to understand. Correlating the statements enables you to link queries without nesting.

To generate dynamic data
Many applications and Web sites identify a session by the current date and time. If you try to replay a script, it will fail because the current time is different than the recorded time. Correlating the data enables you to save the dynamic data and use it throughout the scenario run.

Correlation in Webload
a.Record the script
b.Search for script failures.
c.Check under the DOM view, whether the cookie is saved as a Header or as a Hidden value
- Use any of the following script to capture it,
myCookie = wlHtml.GetHeaderValue("set-cookie")
(or)
myCookie = extractValue("Sessionid=", ";",document.wlHeaders[10].value)
(or)
myCookie = extractValue( "sessionID","/>", document.wlSource)
Use this varibale(myCookie) to replace a dynamic field.
d.Verify that the script is running correctly.

If neccessary it can be explained in detail manner..