LoadRunner Interview Questions

1. Why should you automate Performance Testing?
Ans: Automated Performance Testing is a discipline that leverages products,people, and processes to reduce the risks of application, upgrade, or patch deployment. Automated performance testing is about applying production workloads to pre-deployment systems while simultaneously measuring system performance and end-user experience.

A well-constructed performance test answers questions such as:
* Does the application respond quickly enough for the intended users?
* Will the application handle the expected user load and beyond?
* Will the application handle the number of transactions required by the business?
* Is the application stable under expected and unexpected user loads?
* Are you sure that users will have a positive experience on go-live day?

2. What are the LoadRunner components?
Ans: LoadRunner contains the following components:
* The Virtual User Generator captures end-user business processes and creates an automated performance testing script, also known as a virtual user script.
* The Controller organizes, drives, manages, and monitors the load test.
* The Load Generators create the load by running virtual users.
* The Analysis helps you view, dissect, and compare the performance results.
* The Launcher provides a single point of access for all of the LoadRunner components.

3. What is Scenario?
Ans: A scenario is a file that defines the events that occur during each testing session, based on performance requirements.

4. What is Vusers?
Ans: In the scenario, LoadRunner replaces human users with virtual users or Vusers. A scenario can contain tens, hundreds, or even thousands of Vusers.

5. What is Vuser Script?

Ans: The actions that a Vuser performs during the scenario are described in a Vuser script.

6. What is transaction?
Ans: To measure the performance of the server, you define transactions. A transaction represents end-user business processes that you are interested in
measuring.

7. Tell me about load testing process?
Ans :
* Plan Load Test: Define your performance testing requirements, for example,number of concurrent users, typical business processes and required response times.
* Create Vuser Scripts: Capture the end-user activities into automated scripts.
* Define a Scenario: Use the LoadRunner Controller to set up the load test environment.
* Run a Scenario: Drive, manage, and monitor the load test from the LoadRunner Controller.
* Analyze the Results: Use LoadRunner Analysis to create graphs and reports, and evaluate the performance.

8. What is the default username/password for HP Web Tour Application ?

Ans: Username= jojo and Password = bean. (For Version 9.10)

9. What is the default test script used in loadrunner ?
Ans: demo_scenario.lrs

10. What are the different types of graph present in Loadrunner Controller?
Ans: Runtime graphs, Transaction graphs, Web resource graphs, System Resource graphs, Network graphs, web server resource graphs, Web Application server graphs, database graphs.

11. What are subtypes of Runtime graphs?
Ans: Running vusers, user defined data points, Error Statistics, vusers with Errors.

12. Explain Running Vuser graph?

Ans: Running Vusers - whole scenario graph lets you monitor the number of Vusers that are running at a given time.

13. Explain transaction response time graph?

Ans; Transaction Response Time - whole scenario graph lets you monitor the amount of time it takes for each transaction to be completed.

14. Explain HTTP/Sec graph?
Ans: Hits per Second - whole scenario graph lets you monitor the number of hits (HTTP requests) on the Web server made by Vusers during each second of the scenario run.

15. Explain Windows Resource graphs?
Ans: Windows Resources graph lets you monitor the Windows resource usage measured during a scenario (such as CPU, disk, or memory utilization).

16. Explain Virtual User Generation?
Ans: The LoadRunner Virtual User Generator works on a record-and playback principle. As you walk through a business process on your application, VuGen records your actions into automated scripts which will form the foundation of your load tests.

17. Which language loadrunner uses for scripts?

Ans: LoadRunner uses ANSI C. As your scripts become more advanced, you can leverage C to extend LoadRunner beyond record and playback.

18. What are general run-time settings that apply to all types of scripts?
Ans:
* Run Logic: the number of repetitions
* Pacing: the time to wait between repetitions
* Think Time: the time the user stops to think between steps
* Log: the level of information that you want to gather during playback

19. Explain Correlation ?
Ans: Correlation saves the changing values to a parameter. When running the emulation, the Vuser does not use the recorded value—instead, it uses the new value/session ID, assigned to it by the server.

20. What Component of LoadRunner would you use to play Back the script in multi user mode?
Ans: The Controller component is used to playback the script in multi-user mode. This is done during a scenario run where a vuser script is executed by a number of vusers in a group.

21. What is a rendezvous point?
Ans: You insert rendezvous points into Vuser scripts to emulate heavy user load on the server. Rendezvous points instruct Vusers to wait during test execution for multiple Vusers to arrive at a certain point, in order that they may simultaneously perform a task. For example, to emulate peak load on the bank server, you can insert a rendezvous point instructing 100 Vusers to deposit cash into their accounts at the same time.

22. Explain the recording mode for web Vuser script?
Ans: We use VuGen to develop a Vuser script by recording a user performing typical business processes on a client application. VuGen creates the script by recording the activity between the client and the server. For example, in web based applications, VuGen monitors the client end of the database and traces all the requests sent to, and received from, the database server. We use VuGen to: Monitor the communication between the application and the server; Generate the required function calls; and Insert the generated function calls into a Vuser script.

23. Why do you create parameters?
Ans: Parameters are like script variables. They are used to vary input to the server and to emulate real users. Different sets of data are sent to the server each time the script is run. Better simulate the usage model for more accurate testing from the Controller; one script can emulate many different users on the system.

24. What is correlation? Explain the difference between automatic correlation and manual correlation?
Ans: Correlation is used to obtain data which are unique for each run of the script and which are generated by nested queries. Correlation provides the value to avoid errors arising out of duplicate values and also optimizing the code (to avoid nested queries). Automatic correlation is where we set some rules for correlation. It can be application server specific. Here values are replaced by data which are created by these rules. In manual correlation, the value we want to correlate is scanned and create correlation is used to correlate.

25. How do you find out where correlation is required? Give few examples from your projects?
Ans: Two ways: First we can scan for correlations, and see the list of values which can be correlated. From this we can pick a value to be correlated. Secondly, we can record two scripts and compare them. We can look up the difference file to see for the values which needed to be correlated. In my project, there was a unique id developed for each customer, it was nothing but Insurance Number, it was generated automatically and it was sequential and this value was unique. I had to correlate this value, in order to avoid errors while running my script. I did using scan for correlation.

26. Where do you set automatic correlation options?
Ans: Automatic correlation from web point of view can be set in recording options and correlation tab. Here we can enable correlation for the entire script and choose either issue online messages or offline actions, where we can define rules for that correlation. Automatic correlation for database can be done using show output window and scan for correlation and picking the correlate query tab and choose which query value we want to correlate. If we know the specific value to be correlated, we just do create correlation for the value and specify how the value to be created.

27. What is a function to capture dynamic values in the web Vuser script?
Ans: Web_reg_save_param function saves dynamic data information to a parameter.

28. When do you disable log in Virtual User Generator, When do you choose standard and extended logs?
Ans: Once we debug our script and verify that it is functional, we can enable logging for errors only. When we add a script to a scenario, logging is automatically disabled. Standard Log Option: When you select
Standard log, it creates a standard log of functions and messages sent during script execution to use for debugging. Disable this option for large load testing scenarios. When you copy a script to a scenario, logging is automatically disabled Extended Log Option: Select
extended log to create an extended log, including warnings and other messages. Disable this option for large load testing scenarios. When you copy a script to a scenario, logging is automatically disabled. We can specify which additional information should be added to the extended log using the Extended log options.

29. How do you debug a LoadRunner script?
Ans: VuGen contains two options to help debug Vuser scripts-the Run Step by Step command and breakpoints. The Debug settings in the Options dialog box allow us to determine the extent of the trace to be performed during scenario execution. The debug information is written to the Output window. We can manually set the message class within your script using the lr_set_debug_message function. This is useful if we want to receive debug information about a small section of the script only.

30. How do you write user defined functions in LR? Give me few functions you wrote in your previous project?
Ans: Before we create the User Defined functions we need to create the external library (DLL) with the function. We add this library to VuGen bin directory. Once the library is added then we assign user defined function as a parameter. The function should have the following format: __declspec (dllexport) char* (char*, char*)Examples of user defined functions are as follows:GetVersion, GetCurrentTime, GetPltform are some of the user defined functions used in my earlier project.

31. What are the changes you can make in run-time settings?
Ans: The Run Time Settings that we make are:
a) Pacing - It has iteration count.
b) Log - Under this we have Disable Logging Standard Log and
c) Extended Think Time - In think time we have two options like Ignore think time and Replay think time.
d) General - Under general tab we can set the vusers as process or as multithreading and whether each step as a transaction.

32. Where do you set Iteration for Vuser testing?
Ans: We set Iterations in the Run Time Settings of the VuGen. The navigation for this is Run time settings, Pacing tab, set number of iterations.

33. How do you perform functional testing under load?
Ans: Functionality under load can be tested by running several Vusers concurrently. By increasing the amount of Vusers, we can determine how much load the server can sustain.

34. What is Ramp up? How do you set this?
Ans: This option is used to gradually increase the amount of Vusers/load on the server. An initial value is set and a value to wait between intervals can be specified. To set Ramp Up, go to ‘Scenario Scheduling Options’

35. What is the advantage of running the Vuser as thread? Ans: VuGen provides the facility to use multithreading. This enables more Vusers to be run per generator. If the Vuser is run as a process, the same driver program is loaded into memory for each Vuser, thus taking up a large amount of memory. This limits the number of Vusers that can be run on a single generator. If the Vuser is run as a thread, only one instance of the driver program is loaded into memory for the given number of
Vusers (say 100). Each thread shares the memory of the parent driver program, thus enabling more Vusers to be run per generator.

36. What is the relation between Response Time and Throughput?
Ans: The Throughput graph shows the amount of data in bytes that the Vusers received from the server in a second. When we compare this with the transaction response time, we will notice that as throughput decreased, the response time also decreased. Similarly, the peak throughput and highest response time would occur approximately at the same time.

37. Explain the Configuration of your systems?
Ans: The configuration of our systems refers to that of the client machines on which we run the Vusers. The configuration of any client machine includes its hardware settings, memory, operating system, software applications, development tools, etc. This system component configuration should match with the overall system configuration that would include the network infrastructure, the web server, the database server, and any other components that go with this larger system so as to achieve the load testing objectives.

38. How do you identify the performance bottlenecks?
Ans: Performance Bottlenecks can be detected by using monitors. These monitors might be application server monitors, web server monitors, database server monitors and network monitors. They help in finding out the troubled area in our scenario which causes increased response time. The measurements made are usually performance response time, throughput, hits/sec, network delay graphs, etc.

39. If web server, database and Network are all fine where could be the problem?
Ans: The problem could be in the system itself or in the application server or in the code written for the application.

40. How did you find web server related issues?

Ans: Using Web resource monitors we can find the performance of web servers. Using these monitors we can analyze throughput on the web server, number of hits per second that occurred during scenario, the number of http responses per second, the number of downloaded pages per second.

41. What is the difference between Overlay graph and Correlate graph?
Ans: Overlay Graph: It overlay the content of two graphs that shares a common x-axis. Left Y-axis on the merged graph show’s the current graph’s value & Right Y-axis show the value of Y-axis of the graph that was merged. Correlate Graph: Plot the Y-axis of two graphs against each other. The active graph’s Y-axis becomes X-axis of merged graph. Y-axis of the graph that was merged becomes merged graph’s Y-axis.

42. How did you plan the Load? What are the Criteria?
Ans: Load test is planned to decide the number of users, what kind of machines we are going to use and from where they are run. It is based on 2 important documents, Task Distribution Diagram and Transaction profile. Task Distribution Diagram gives us the information on number of users for a particular transaction and the time of the load. The peak usage and off-usage are decided from this Diagram. Transaction profile gives us the information about the transactions name and their priority levels with regard to the scenario we are deciding.

43. What does vuser_init action contain?

Ans: Vuser_init action contains procedures to login to a server.

44. What does vuser_end action contain?
Ans: Vuser_end section contains log off procedures.

45. What is think time? How do you change the threshold?
Ans: Think time is the time that a real user waits between actions. Example: When a user receives data from a server, the user may wait several seconds to review the data before responding. This delay is known as the think time. Changing the Threshold: Threshold level is the level below which the recorded think time will be ignored. The default value is five (5) seconds. We can change the think time threshold in the Recording options of the Vugen.

46. What is the difference between standard log and extended log?
Ans: The standard log sends a subset of functions and messages sent during script execution to a log. The subset depends on the Vuser type Extended log sends a detailed script execution messages to the output log. This is mainly used during debugging when we want information about: Parameter substitution. Data returned by the server. Advanced trace.

47. Explain the following functions: - lr_debug_message
Ans: The lr_debug_message function sends a debug message to the output log when the specified message class is set. lr_output_message - The lr_output_message function sends notifications to the Controller Output window and the Vuser log file. lr_error_message - The lr_error_message function sends an error message to the LoadRunner Output window. lrd_stmt - The lrd_stmt function associates a character string (usually a SQL statement) with a cursor. This function sets a SQL statement to be processed. lrd_fetch - The lrd_fetch function fetches the next row from the result set.

48. Explain Throughput?
Ans: If the throughput scales upward as time progresses and the number of Vusers increase, this indicates that the bandwidth is sufficient. If the graph were to remain relatively flat as the number of Vusers increased, it would be reasonable to conclude that the bandwidth is constraining the volume of data delivered.

49. Types of Goals in Goal-Oriented Scenario
Ans: Load Runner provides you with five different types of goals in a goal oriented scenario:
* The number of concurrent Vusers
* The number of hits per second
* The number of transactions per second
* The number of pages per minute
* The transaction response time that you want your scenario

50. Explain Analysis Scenario (Bottlenecks)?
Ans: In Running Vuser graph correlated with the response time graph you can see that as the number of Vusers increases, the average response time of the check itinerary transaction very gradually increases. In other words, the average response time steadily increases as the load
increases. At 56 Vusers, there is a sudden, sharp increase in the average response time. We say that the test broke the server. That is the mean time before failure (MTBF). The response time clearly began to degrade when there were more than 56 Vusers running simultaneously.