Lesson 2: Preparing Your Script for Replay
After you create a Vuser script, you validate it by running it from VuGen. Sometimes a replay will fail,
even though the same actions succeeded during the recording.
Many applications use dynamic values that change each time you use the application. For example,
some servers assign a unique session ID for every new session. When you try to replay a recorded
session, the application creates a new session ID that differs from the recorded session ID. Dynamic
values, such as these unique session IDs, may pose difficulties when you replay specific types of Vuser
scripts. For example, dynamic session IDs often pose problems when replaying Web-HTTP/HTML
scripts, but not when replaying TruClient scripts.
LoadRunner uses correlations to address the issue of dynamic values. When you correlate a value,
VuGen saves the changing values, in our case the session ID, to a parameter. When running the Vuser
script, the Vuser does not use the recorded value—instead, it uses the new session ID, assigned to it by
the server.
For scripts that contain dynamic parameters, such as session IDs, VuGen automatically prompts you at
the end of the recording to correlate the values. In the previous lesson, we bypassed the correlations, in
order to view the script as is.
In this lesson you will learn how to correlate the dynamic values, and facilitate a successful replay.
How do I correlate my script?
If you try to replay the unmodified Vuser script that you recorded in "Lesson 1: Building a Vuser Script"
on page11, the replay will fail. The new session IDwill not match the recorded ID, and this will cause a
failure.
To overcome this issue, you use VuGen's Design Studio to correlate the session ID. Normally, VuGen
scans the script at the end of the recording session and prompts you with the suggested correlations.
However, you can open the Design Studio at any time to scan the script for correlations. You can also
undo any correlation that you did via the Design Studio.
1. Open the Design Studio.
Click the toolbar's Design Studio button, or select Design > Design Studio.
VuGen scans the script and its associated data, searching for possible dynamic values.
2. Correlate the Session ID.
a. Select the Session ID entry in the Correlation tab, and click Correlate. VuGen changes the status
of the Session ID to Applied, and inserts a new function at the top of the Vuser script. The new
function saves the original session ID to a parameter.
b. Close the Design Studio.
3. Examine the syntax of the correlation statement.
In the VuGen editor, locate the function that VuGen added to the beginning of the script. The new
entry has the following format:
LoadRunner Tutorial
Lesson 2: Preparing Your Script for Replay
LoadRunner (12.56 and 12.57) Page 18 of 86