In Controller, you define a number of Vusers (excluding GUI Vusers) to generate load on a server by submitting input directly to the server. Vusers do not operate client applications—they access the server using LoadRunner API functions. These API functions emulate the input from an actual application.
Because Vusers are not reliant on client software, you can use Vusers to test server performance even before the client software has been developed. Since Vusers do not have a user interface, the amount of system resources required is minimal. This allows you to run large numbers of Vusers on a single workstation.
The following example illustrates the use of Vusers in a scenario: Suppose that you have a Web-based database server that maintains your customer information. The information is accessed by numerous customer service personnel who are located throughout the country. The server receives the queries, processes the requests, and returns responses via the Web to field personnel.
You want to test the response times of the entire system when numerous service personnel simultaneously access the server. Using LoadRunner, you could create a scenario with several hundred Vusers, each one accessing the server database. The Vusers enable you to emulate and measure the performance of your database and Web servers under the load of many users.
To emulate the Vusers, you create a script to define their actions. A Vuser script includes functions that control the script execution and specify the input that the Vuser submits to the server. For more information, see Vusers.
For the database server example above, you could create a Vuser script that performs the following actions:
Logs in to the Web application
Connects to the database server
Submits an SQL query
Retrieves and processes the server response
Disconnects from the server and the Web