LoadRunner Interview Questions and Best Answers
Q #1. What is the difference between Performance testing and Performance
Ans => In Performance testing, testing cycle includes requirement gathering, scripting,
execution, result sharing and report generation. Performance Engineering is a step
ahead of Performance testing where after execution; results are analyzed with the aim to
find the performance bottlenecks and the solution is provided to resolve the identified
Q #2. Explain Performance Testing Life Cycle.
Ans => Step 1: System Analysis (Identification of critical transaction)
Virtual User Generator
Step 2: Creating Virtual User Scripts (Recording)
Step 3: Defining Users Behavior (Runtime setting)
Step 4: Creating Load Test Scenarios
Step 5: Running the Load Test Scenarios and Monitoring the Performance
Step 6: Analyzing the Results
Refer Performance Testing Tutorial #2 for more details.
Q #3. What is Performance testing?
Ans => Performance testing is done to evaluate application`s performance under load
and stress conditions. It is generally measured in terms of response time of user’s action
Q #4. What is Load testing?
Ans => Load testing is to determine if an application can work well with the heavy
usage resulting from a large number of users using it simultaneously. Load is increased
to to simulates the peak load that the servers are going to take during maximum usage
Q #5. What are the different components of LoadRunner?
Ans => The major components of LoadRunner are:
VUGen- Records Vuser scripts that emulate the actions of real users.
Controller – Administrative center for creating, maintaining and executing load test
scenarios. Assigns scenarios to Vusers and load generators, starts and stops loading
Load Generator – An agent through which we can generate load
Analysis – Provides graphs and reports that summarize the system performance
Q #6. What is the Rendezvous point?
Ans => Rendezvous point helps in emulating heavy user load (request) on the server.
This instructs Vusers to act simultaneously. When the vuser reaches the Rendezvous
point, it waits for all Vusers with Rendezvous point. Once designated numbers of Vusers
reaches it, the Vusers are released. Function lr_rendezvous is used to create the
Rendezvous point. This can be inserted by:
1. Rendezvous button on the floating Recording toolbar while recording.
2. After recording Rendezvous point is inserted through Insert> Rendezvous.
Q #7. What are the different sections of the script? In what sequence does
these section runs?
Ans => LoadRunner script has three sections vuser_init, Action and vuser_end.
vuser_init has requests/actions to login to the application/server.
Action has actual code to test the functionality of the application. This can be played
many times in iterations.
Vuser_end has requests/actions to login out the application/server.
The sequence in which these sections get executed is vuser_init is at the very beginning
and vuser_end at the very end. Action is executed in between the two.
Q #8. How do you identify which protocol to use for any application?
Ans => Previously Performance tester had to depend much on the development team to
know about the protocol that application is using to interact with the server. Sometimes,
it also used to be speculative.
However, LoadRunner provides a great help in form of Protocol Advisor from version
9.5 onwards. Protocol advisor detects the protocols that application uses and suggest us
the possible protocols in which script can be created to simulate the real user.
Q #9. What is correlation? Explain the difference between automatic correlation
and manual correlation?
Ans => Correlation is used to handle the dynamic values in a script. The dynamic value
could change for each user action (value changes when action is replayed by the same
user) or for different users (value changes when action is replayed with different user).
In both the cases correlation takes care of these values and prevents them from failing
Manual Correlation involves identifying the dynamic value, finding the first occurrence of
dynamic value, identifying the unique boundaries of capturing the dynamic value, writing
correlation function web_reg_save_param before the request having the first occurrence
of dynamic value in its response.
Automated correlation works on predefined correlation rules. The script is played back
and scanned for auto correlation on failing. Vugen identifies the place wherever the
correlation rules work and correlate the value on approval.
Refer this tutorial for more details.
Q #10. How to identify what to correlate and what to parameterize?
Ans => Any value in the script that changes on each iteration or with different user
while replaying needs correlation. Any user input while recording should be
Q #11. What is parameterization & why is parameterization necessary in the
Ans => Replacing hard coded values within the script with a parameter is called
Parameterization. This helps a single virtual user (vuser) to use different data on each
run. This simulates real life usage of application as it avoids server from caching results.
Refer this tutorial for more details.
Q #12. How you identify Performance test use cases of any application?
Ans => Test cases/Uses cases for Performance test are almost same as any
manual/functional testing test cases where each and every step performed by the user is
written. The only difference is that all manual test cases can’t be Performance testing
use cases as there are few criteria for the selection as:
I. The user activity should be related to critical and most important functionality of the
II. The user activity should be having good amount of database activity such as search,
delete or insert.
III. The user activity should be having good user volume. The functionality having less
user activity is generally omitted from Performance testing point of view. e.g admin
Any of the manual test cases that fulfill the above criteria can be used as performance
testing use case/test case. If manual test cases are not written step by step ,
Performance team should create dedicated documents for them.
Q #13. While scripting you created correlation rules for automatic correlation.
If you want to share the correlation rules with your team member working on
the same application so that he/she can use the same on his workstation, how
will you do that?
Ans => Correlation rules can be exported through .cor file and the same file can be
imported through VuGen.
-----------Q #14. What are different types of vuser logs which can be used while scripting
and execution? What is the difference between these logs? When you disable
Ans => There are two types of Vuser logs available –Standard log and Extended log.
Logs are key for debugging the script. Once a script is up and running, logging is
enabled for errors only. Standard log creates a log of functions and messages sent to the
server during script execution whereas Extended log contains additional of warnings and
other messages. Logging is used during debugging and disabled while execution.
Logging can be enabled for errors in that case.
Q #15. What is Modular approach of scripting?
Ans => In Modular approach, a function is created for each request (e.g. login, logout,
save, delete, etc.) and these functions are called wherever required. This approach gives
more freedom to reuse the request and saves time. With this approach it is
recommended to work with web custom request.
Q #16. What are the different types goals in Goal-Oriented Scenario?
Ans => LoadRunner has five different types of goals in Goal-Oriented Scenario. These
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
Q #17. How is each step validated in the script?
Ans => Each step in the script is validated with the content on the returned page. A
content check verifies whether specific content is present on the web page or not. There
are two types of content check which can be used in LoadRunner:
Text Check- This checks for a text/string on the web page
Image Check- This checks for an image on a web page.
Q #18. How is VuGen script modified after recording?
Ans => Once the script is recorded, it can be modified with the following process:
Q #19. What is Ramp up and Ramp Down?
Ans => Ramp up- Rate at which virtual users add to the load test
Ramp Down- Rate at which virtual users exit from the load test.
Q #20. What is the advantage of running the Vuser as thread?
Ans => Running vusers as thread helps generate more virtual users from any machine
due to small memory print of the vuser running as thread.
Q #21. What is wasted time in VuGen Replay log?
Ans => Waste time is never performed by any browser user and just the time spent on
the activities which support the test analysis. These activities are related to logging,
keeping record and custom analysis.
Q #22. How do you enable text and image checks in VuGen?
Ans => This can be done by using functions web_find (for text check) and
web_image_check (for image check) and enabling image and text check from run time
Run Time Setting–>Preference–>Enable the Image and text check box.
Q #23. What is the difference between web_reg_find and web_find?
Ans => web_reg_find function is processed before the request sent and is placed before
the request in the VuGen script whereas web_find function is processed after the
response of the request come and is placed after the request in VuGen script.
Q #24. What are the challenges that you will face to script the step “Select All”
and then “Delete” for any mail account?
Ans => In this case the post for “Select All” and “Delete” will change every time
depending on the number mails available. For this the recorded request for the two
should be replaced with custom request and string building is required to build the post.
(Note- This question needs practical knowledge. So please this practically and formulate
Q #25. What is difference between pacing and think time?
Ans => Pacing is wait time between the action iterations whereas think time is wait time
between the transactions.
Q #26. What are the number of graphs you can monitor using Controller at a
time? What is the max of them?
Ans => One, two, four and eight graphs can be seen at a time. The maximum number
of graphs can be monitored in at a time is 8.
Q #27. You have an application which shows the exam results of the student.
Corresponding to name of each student its mentioned whether he passed or
failed the exam with the label of “Pass” and “Fail”. How will you identify the
number of passed and failed student in VuGen script?
Ans => For this text check is used for the web page for the text “Pass and “Fail”.
Through the function web_reg_find, we can capture the number of texts found on the
web page with the help of “SaveCount”. SaveCount stored the number of matches
found. For example-
Q #28. During the load test what is the optimum setting for Logs?
Ans => For the load test log level is set to minimal. This can be achieved with setting
the log level to the standard log and selecting the radio button “Send message only
when an error occurs”.
Q #29. How will you handle the situation in scripting where for your mailbox
you have to select any one mail randomly to read?
Ans => For this we will record the script for reading the first mail. Try to find what is
being posted in the request to read the first mail such as mail ids or row no. From the
post where a list of mails is reflecting, we will try to capture all the email ids row no with
correlation function and keeping Ordinal as All i.e. ORD=All . Replace the requested
email id in the read post with any of the randomly selected email id from the list of
captured email ids.
Refer this Scripting Tutorial.
Q #30. What is the Think Time? What is the Threshold level for think time and
how can be this changed?
Ans => Think time is the wait time inserted intentionally between the actions in the
script to emulate real user`s wait time while performing activity on the application. The
Threshold level for Think time in the level below which recorded think time will be
ignored. This can be changed from Recorded options->Script->Generate think time
greater than threshold.
Q #31. How is Automated Correlation configured?
Ans => Any setting related to Automated Correlation can be done byGeneral Options>Correlation. Correlation rules are set fromRecording options->Correlations.
Q #32. How you decide the number of load generator machine required to run a
Ans => Number of load generator required totally depends on the protocol used to
create the script and configuration of the load generator machine. Each protocol has
different memory print and this decides how many virtual users can be generated from
the give configuration of the machine (load generator).
Q #33. What are the capabilities exactly you look for while selecting the
performance testing tool?
Ans => Performance testing tool should capable of:Testing an application built using multiple technologies and hardware platforms.
Determine the suitability of a server for testing the application
Testing an application with load of tens, thousand and even thousands virtual
Q #34. How concurrent users are differing from simultaneous users?
Ans => All simultaneous users are concurrent users but vice versa is not true.
All the vusers in the running scenario are Concurrent users as they are using the same
application at the same time but may be or may not be doing the same tasks.
Simultaneous users perform the same task at the same time. Concurrent users are made
Simultaneous users through rendezvous points. Rendezvous points instruct the system
to wait till a certain number of vusers arrive so that they all can do a particular task
Q #35. How do you identify which values need to be correlated in the script?
Give an example.
Ans => This can be done in ways:
a) Record the two scripts with similar steps and compare them using WDiff utility. (See
b) Replay the recorded script and scan for correlation. This gives a list of values that can
Session Id is a good example of this. When two scripts are recorded and compared using
WDiff utility. Session ids in the two scripts should be different and WDiff highlight these
Q #36. How does caching affect performance testing results?
Ans => When data is cached in server`s memory, the server need not fetch the result
and no server activity triggered. Test result does not reflect the same performance of
real user using the application with different data.
Q #37. How will you stop the execution of script on error?
Ans => This can be achieved through lr_abort function. The function instructs the vuser
to stop executing Action section and end the execution by executing the vuser_end
section. This function is helpful in handling a specific error. This can also be used to
handle a situation rather than error where execution is not possible. The function
assigned “Stopped” status to the vuser which stopped due to lr_abort function. In RunTime setting, “Continue on error” should be unchecked.