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1. What is load testing?
Answer: Load testing is to
test that if the application works fine with the loads that
result from large number of simultaneous users, transactions
and to determine weather it can handle peak usage periods.
2. What is Performance
testing?
Answer: Timing for both read
and update transactions should be gathered to determine whether
system functions are being performed in an acceptable timeframe.
This should be done standalone and then in a multi user environment
to determine the effect of multiple transactions on the timing
of a single transaction.
3. Explain the
Load testing process?
Answer: Following are the
steps involved in the Load testing process:
Step 1: Planning
the test - Here,
we develop a clearly defined test plan to ensure the test
scenarios we develop will accomplish load-testing objectives.
Step 2: Creating
Vusers - Here,
we create Vuser scripts that contain tasks performed by each
Vuser, tasks performed by Vusers as a whole, and tasks measured
as transactions.
Step 3: Creating
the scenario -
scenario describes the events that occur during a testing
session. It includes a list of machines, scripts, and Vusers
that run during the scenario. We create scenarios using LoadRunner
Controller. We can create manual scenarios as well as goal-oriented
scenarios. In manual scenarios, we define the number of Vusers,
the load generator machines, and percentage of Vusers to be
assigned to each script. For web tests, we may create a goal-oriented
scenario where we define the goal that our test has to achieve.
LoadRunner automatically builds a scenario for us.
Step 4: Running
the scenario - We
emulate load on the server by instructing multiple Vusers
to perform tasks simultaneously. Before the testing, we set
the scenario configuration and scheduling. We can run the
entire scenario, Vuser groups, or individual Vusers.
Step 5: Monitoring
the scenario - We
monitor scenario execution using the LoadRunner online runtime,
transaction, system resource, Web resource, Web server resource,
Web application server resource, database server resource,
network delay, streaming media resource, firewall server resource,
ERP server resource, and Java performance monitors.
Step 6: Analyzing
test results - During
scenario execution, LoadRunner records the performance of
the application under different loads. We use LoadRunner
graphs and reports to analyze the application performance.
4. When do you
do load and performance Testing?
Answer: We perform load testing
once we are done with interface (GUI) testing. Modern system
architectures are large and complex. Whereas single user testing
primarily on functionality and user interface of a system component,
application testing focuses on performance and reliability of
an entire system. For example, a typical application-testing
scenario might depict 1000 users logging in simultaneously to
a system. This gives rise to issues such as what is the response
time of the system, does it crash, will it go with different
software applications and platforms, can it hold so many hundreds
and thousands of users, etc. This is when we set do load and
performance testing.
5. What are the
components of LoadRunner?
Answer: The components of
LoadRunner are The Virtual User Generator, Controller, and the
Agent process, LoadRunner Analysis and Monitoring, LoadRunner
Books Online.
6. What Component
of LoadRunner would you use to record a Script?
Answer: The Virtual User Generator
(VuGen) component is used to record a script. It enables you
to develop Vuser scripts for a variety of application types
and communication protocols.
7. What Component
of LoadRunner would you use to play Back the script in multi
user mode?
Answer: The Controller component
is used to playback the script in multi-user mode. This is done
during a scenario run where a vuserscript is executed by a number
of vusers in a group.
8. What is a rendezvous
point?
Answer: 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.
9. What is a scenario?
Answer: A scenario defines
the events that occur during each testing session. For example,
a scenario defines and controls the number of users to emulate,
the actions to be performed, and the machines on which the virtual
users run their emulations.
10. Explain the
recording mode for web Vuser script?
Answer: 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.
11. Why do you
create parameters?
Answer: 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 emulte many different users on the system.
12. What is correlation?
Explain the difference between automatic correlation and manual
correlation?
Answer: 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.
13. How do you
find out where correlation is required? Give few examples from
your projects?
Answer: 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.
14. Where do you
set automatic correlation options?
Answer: 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.
15. What is a function
to capture dynamic values in the web Vuser script?
Answer: Web_reg_save_param
function saves dynamic data information to a parameter.
16. When do you
disable log in Virtual User Generator, When do you choose standard
and extended logs?
Answer: 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.
17. How do you
debug a LoadRunner script?
Answer: 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.
18. How do you
write user defined functions in LR? Give me few functions you
wrote in your previous project?
Answer: 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* <function name>(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.
19. What are the
changes you can make in run-time settings?
Answer: 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.
20. Where do you
set Iteration for Vuser testing?
Answer: 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.
21. Did u use LoadRunner? What version?
Answer: - Yes. Version 8.0.
22. How do you perform functional testing under load?
Answer: 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.
23. What is Ramp up? How do you set this?
Answer: 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’
24. What is the advantage of running the Vuser as thread?
Answer: 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.
25. If you want to stop the execution of your script on error, how do you do that?
Answer: The lr_abort function aborts the execution of a Vuser script. It instructs the Vuser to stop executing the Actions section, execute the vuser_end section and end the execution. This function is useful when you need to manually abort a script execution as a result of a specific error condition. When you end a script using this function, the Vuser is assigned the status "Stopped". For this to take effect, we have to first uncheck the .Continue on error. option in Run-Time Settings.
26. What is the relation between Response Time and Throughput?
Answer: 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.
27. Explain the Configuration of your systems?
Answer: 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.
28. How do you identify the performance bottlenecks?
Answer: 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.
29. If web server, database and Network are all fine where could be the problem?
Answer: The problem could be in the system itself or in the application server or in the code written for the application.
30. How did you find web server related issues?
Answer: 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.
31. How did you find database related issues?
Answer: By running .Database. monitor and help of .Data Resource Graph. we can find database related issues. E.g. You can specify the resource you want to measure on before running the controller and than you can see database related issues
32. Explain all the web recording options?
33. What is the difference between Overlay graph and Correlate graph?
Answer: 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.
34. How did you plan the Load? What are the Criteria?
Answer: 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.
35. What does vuser_init action contain?
Answer: Vuser_init action contains procedures to login to a server.
36. What does vuser_end action contain?
Answer: Vuser_end section contains log off procedures.
37. What is think time? How do you change the threshold?
Answer: 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.
38. What is the difference between standard log and extended log?
Answer: 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.
39. Explain the following functions: - lr_debug_message - The lr_debug_message function sends a debug message to the output log when the specified message class is set.
Answer: 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.
40. Throughput
- 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.
41. Types of Goals in Goal-Oriented Scenario
Answer: 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
42. Analysis Scenario (Bottlenecks)
Answer: 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.
43. What is correlation? Explain the difference between automatic correlation and manual correlation?
Answer: 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.
44. Where do you set automatic correlation options?
Answer: 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.
45. What is a function to capture dynamic values in the web vuser script?
Web_reg_save_param function saves dynamic data information to a parameter.
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