In my webservices test plan, I am sending SOAP request to create user and it sends back username and unique id in the response data. I want to save that username and uniqueid in
You can use sample_variables
property to store custom variables values into .jtl results file.
Add the following line to user.properties file (it lives under /bin folder of your JMeter installation)
sample_variables=username,password
You will see variables values within .jtl results file upon execution.
See Default Configuration chapter for explanation and Apache JMeter Properties Customization Guide for more information on different JMeter properties and ways of setting and/or overriding them.