1. What is load testing?
- 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?
-
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. Did u use LoadRunner? What version?
- Yes. Version x.x .
4. Explain 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. A 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’s graphs and reports to analyze the application’s
performance.
5. When do you do load and performance Testing?
-
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.
6. What are the components of LoadRunner?
-
The components of LoadRunner are The Virtual User Generator,
Controller, and the Agent process, LoadRunner Analysis and Monitoring,
LoadRunner Books Online.
7. What Component of LoadRunner would you use to record a Script?
-
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.
8. What Component of LoadRunner would you use to play Back the script. in multi user mode?
-
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.
9. What is a rendezvous point?
-
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.
10. What is a scenario?
- 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.
11. Explain the recording mode for web Vuser script?
-
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.
12. Why do you create parameters?
-
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.
13. What is correlation?
Explain
the difference between automatic correlation and manual correlation? -
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.
14. How do you find out where correlation is required? Give few examples from your projects?
-
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.
15. Where do you set automatic correlation options?
-
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.
16. 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.
17. When do you disable log in Virtual User Generator, When do you choose standard and extended logs?
-
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
selectStandard 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: Selectextended
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.
18. How do you debug a LoadRunner script?
-
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.
19. How do you write user defined functions in LR?
Give
me few functions you wrote in your previous project? - 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.
20. What are the changes you can make in run-time settings?
-
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.
21. Where do you set Iteration for Vuser testing?
-
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.
22. How do you perform. functional testing under load?
-
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?
-
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 bespecified. To set Ramp Up, go to ‘Scenario Scheduling
Options’
24. What is the advantage of running the Vuser as thread?
-
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?
-
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?
-
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?
-
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?
-
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?
- 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?
-
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?
-
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?
-
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?
-
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?
- Vuser_init action contains procedures to login to a server.
36. What does vuser_end action contain?
- Vuser_end section contains log off procedures.
37. What is think time? How do you change the threshold?
-
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?
-
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.
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
- 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):
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? -
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?
-
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.