it's all about the Performance Testing
LoadRunner works by creating virtual users who take the place of real users operating client software, such as Internet Explorer sending requests using the HTTP protocol to IIS or Apache web servers.
Requests from many virtual user clients are generated by “Load Generators” in order to create a load on various servers under test
These load generator agents are started and stopped by the “Controller” program.
The Controller controls load test runs based on “Scenarios” invoking compiled “Scripts” and associated “Run-time Settings”.
Scripts are crafted using the “Virtual user script Generator” (named “V U Gen”), It generates C-language script code to be executed by virtual users by capturing network traffic between Internet application clients and servers.
With Java clients, VuGen captures calls by hooking within the client JVM.
During runs, the status of each machine is monitored by the Controller.
At the end of each run, the Controller combines its monitoring logs with logs obtained from load generators, and makes them available to the “Analysis” program, which can then create run result reports and graphs for Microsoft Word, Crystal Reports, or an HTML webpage browser.
Each HTML report page generated by Analysis includes a link to results in a text file which Microsoft Excel can open to perform additional analysis.
Errors during each run are stored in a database