Note: Please understand the tool and its functionalities thoroughly before proceeding to the above Interview Questions
Q1. What is Load Testing?
Ans: 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
Q2. What is Performance testing?
Ans: Timing for both read and update transactions should be gathered to determine whether system functions are being performed in an acceptable time frame. This should be done stand alone and then in a multi user environment to determine the effect of multiple transactions on the timing of a single transaction
Q3. Did you use Loarunner? What version?
Ans: Yes, 11.0
Q4. Explain the Load testing process.
Ans: Step 1: Planning the test
Here, we develop clearly defined test plan to ensure that test scenarios we create will accomplish load-testing objectives
Step 2: Creating Vusers
In this step Vuser scripts are created 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 build a scenario for us.
Step 4: Running the scenario
We emulate load on the server by instructing multiple Vusers to perform tasks simultaneoulsy. 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.
Q5. When do you do performance testing?
Ans: We perform load testing once we are done with interface (GUI) testing. Modern system architectures are large and complex. Where as 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 hundereds and thousands of users, etc. This is when we set do load and performance testing
Q6. What are the components of Loadrunner?
Ans: The components of Loadrunner are 1) The Virtual User (Vuser) Generator 2) Controller and 3) Analyzer
Q7. What component of Loadrunner would you use to record a script?
Ans: The Virtual User Generator (VuGen) component is used to record a script. It enables to develop Vuser scripts for a variety of application types and communication protocols
Q8. 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
Q9. What is rendezvous point?
Ans: Rendezvous point is inserted in the 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
Q10. What is a scenario?
Ans: 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.
Q11. 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 send to, and received from, the database server.
We use Vugen to:
a) Monitor the communication between the application and the server
b) Generate the required function calls and
c) Insert the generated function calls into a Vuser script
Q12. 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
Main reasons to create parameters are
a) Different sets of data are sent to the server each time the script is run
b) Better simulate the usage model for more accurate testing from the Controller; one script can emulate many different users on the system.
Q13. 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 correaltion 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.
Q14. How do you find out where correlation is required? Give few examples from your projects?
Ans: There are two ways to find correlation
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 insurance number, it was generated automatically and it was sequential and this was unique. I had to correlate this value, in order to avoid eroors while running my script. I did using scan for correlation
Q15. 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 message 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 need to create correlation for the value and specify how the value to be created.
Q16. What is a function to capture dynamic values in the web Vuser script?
Ans: web_reg_param function saves dynamic data information to a parameter
Q17. 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 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 send 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 warning 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 speicify which additional information should be added to the extended log using the Extended log options
Q18. How to 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.
Q19. How do you write user defined functions in Loadrunner? Give a few functions?
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 above format:
_declspec (dllexport) char* (char*, char*)
Examples of user defined functions are above:
Get Version, GetCurrentTime, GetPltform are some of the user defined functions are the examples
Q20. 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 Extended
c) 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
Q21. Where do you set Iteration for Vuser testing?
Ans: We set iterations in the run time settingd of the VuGen. The navigation for this is run time settings --> Pacing tab --> set number of iterations.
Q22. How to 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
Q23. What is Ramp up? How to set this?
Ans: This option is used to gradually increase the amount of Vusers/load on the sercer. An initial value is set and a value to wait between intervals can be specified. To set Ramp up, go to 'Scenario Scheduling Options'
Q24. What is the advantage of running the Vuser as thread?
Ans: VuGen provides the facility to use multi threading. 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.
Q25. If you want to stop the execution of the script on error, how do you do that?
Ans: 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.
Q26. What is the relation between Response time and Throughput?
Ans: Throughput graph shows the amount of data in bytes that the Vusers recived from the server in a second. When we compare this with the transaction reponse time, we will notice that as throughput decreased. Similarly the peak throughput and highest reponse time would occur approximately at the same time.
Q27. Explain the configuration of your system?
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.
Q28. How do you identify the performance bottlenecks?
Ans: Performacne Bottlenecks can be detected by using monitors. These monitors might be application server monitors, web server monitors, database server monitors and network moniotrs. They help in finding out the troubled area in our scenario which causes increased response time. The measurements made are usually performance reponse time, throughput, hits/sec, network delay graphs, etc.
Q29. 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.
Q30. How did you find web server realted issues?
Ans: Using web resource monitors we can find the performance of web servers. Using these monitors we can analyze thoroughput on the web server, number of hits per second that occured during scenario, the number of http reponses per second, the number of downloaded pages per second.
Q31. How id you find database releated issues?
Ans: By running "Database" monitor and help of "Data Resource Graph" we can find database related issues. For an example we can specify the resource you want to measure on before running the controller and then you can see database related issues
Q32. Explain all the web recording options.
Ans:
Q33. What is the difference between Overlay graph and Correlate graph?
Ans: Overlay Graph: It overlays 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 and 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 graph's y-axis
Q34. How do 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 two important documents. They are 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 inforamtion about the transactions name and their priority levels with regard to the scenario we are deciding.
Q35. What does vuser_init action contain?
Ans: Vuser_init action contains procedures to login to a server.
Q36. What does vuser_end action contain?
Ans: Vuser_end section contains log off procedures
Q37. What is think time? How can 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.
Q38. What is the difference between standard and extended log?
Ans: Standard log: It sends a subset of functions and messages send during script extended to a log. The subset depends on the Vuser type.
Extended log: It sends a detailed script execution messages to the output log. This mainly used during debugging when we want information about:
a) Parameter substitution
b) Data returned by the server
c) Advance trace
Q39. Explain the above functions:
Ans:
a) lr_debug_message
The lr_debug_message function sends a debug message to the output log when the specified message class is set
b) lr_output_message
The lr_output_message function sends notifications to the controller output window and the Vuser log file
c) lr_error_message
The lr_error_message function sends an error message to the loadrunner output window
d) 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
e) lrd_fetch
The lrd_fetch function fetches the next row from the result set
Q40. Explain about Throughput?
Ans: If the troughput 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.
Q41. What are the types of Goals in Goal-oriented Scenario?
Ans: Loadrunner provides with five differenet types of goals in a goal oriented scenario:
1) The number of concurrent Vusers
2) The number of hits per second
3) The number of transactions per second
4) The number of pages per minute
5) The transaction response time
Analysis Scenario (Bottlenecks):
In running Vuser graph correlated with the response time graph one 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 fifty six Vusers, there is a sudden, sharp increase in the average response time. We say that the test broke the server. That is mean time before failure (MTBF). The response time clearly began to degrade when there were more than fifty six Vusers running simultaneously
Q42. 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
Q43. What are the three sections of a Vuser script and what is the purpose of each one?
Ans: 1) Vuser_init - used for recording the logon
2) Actions - used for recording the business process
3) Vuser_end - used for recording the logoff
Q44. For what purpose are Vusers created?
Ans: Vusers are created to emulate real users acting on the server for the purpose of load testing
Q45. What are the beifits of multiple action files within a Vuser?
Ans: They allow to perform different business processes in one Vuser to represent a real user who does the ame thing. They let you build Vusers that emulate real users defined in the User Community profile. They also allow you to record the login and logoff separately from the Action files and thus to avoid iteration
Q46. How can you tell the difference between an integer value and a string value in a Vugen script?
Ans: Strings are enclosed in quotes; integers are not
Q47. What is the purpose of loadrunner transaction?
Ans: Loadrunner transaction is to measure one or more steps/user actions of a business process
Q48. What is the easiest way to get measurements for each step of a recorded script?
Ans: For entire action file? Enable automatic transactions (Runtime settings, Recording Options)
Q49. When would you parameterize a value rather than correlate queries?
Ans: Parameterize a value only when it is input by the user
Q50. What are the four selection methods when choosing data from a data file?
Ans: Sequential, Random, Unique and same line as
Q51. How can reusing the same data during iterative execution of a business process negatively affect load testing results?
Ans: In reusing the same data for each iteration, the server recognizes the same data is requested and places it in its cache. The load test then gets performance results that are not based on real server activity but caching. This will not provide the correct results during the analysis of the load test.
Q52. How can caching negatively affect load testing results?
Ans: When data is cached in the server's memory, the server does not need to fetch it from the database during playback. Then, test results do not reflect the same performance they would if real users were loading the system with different data
Q53. Why is it recommeneded to add verification checks to the Vusers?
Ans: If we want to verify, using loadrunner that the business process is functioning as expected under load
Q54. When does VuGen record a web_submit_data instead of a web_submit_form? Why? (Be as specific as possible)
Ans: A web_submit_data is recorded when Vugen cannot match the action, method, data fields, and/or hidden data values with the page that is stored in the record proxy cache. Comparison failures are typically caused by something other than HTML setting the properties of the HTTP request. Because VuGen can parse only HTML, it cannot find all the properties of the HTTP request in memory. This results in the hard coding of all the request information in a web_submit_data statement.
Q55. What do you need to do to be able to view parameter substitution in the execution log?
Ans: Check extended log and parameter substitution in the Run-time settings
Q56. How can you determine which field is data dependent?
Ans: Re-record the same script using different input values, and then compare the two scripts
Q57. Where should the rendezvous be placed in the script?
Ans: The rendezvous should be placed immediately before the transaction where you want to create peak load. In this case, the rendezvous should be placed right before starting the update order transaction
Q58. For what purpose should you select continue on error?
Ans: Set it only when making execution logs more descriptive or adding logic to the vuser
Q59. What is the purpose of selecting show browser during replay in the general options settings?
Ans: This setting allows to see the pages that appear during playback. This is useful for debugging Vuser during the initail stages of web Vuser creation
Q60. What tools does vugen provide to help to analyze vuser run results?
Ans: Execution Log, Run-Time Viewer and Mercury Test results window
Q61. If your Vuser script had two parameters, "DepartCity" and "Arrival City" how could you have the vuser script return an error message which included the city names?
Ans: lr_error_message ("The Vuser could not submit the reservation request for "%s to %s", (lr_eval_string("{DepartCity}"), lr_eval_string("{ArrivalCity}"));
Q62. Why should you run more Vusers than your anticipated peak load?
Ans: (1) To test the scalability of the system
(2) To see what happenes when there is a spike in system usage
Q63. What is the difference between manual scenario and Goal oriented scenario? How Goal oriented scenarios can be created?
Ans: Manual Scenario:
--> Main purpose is to learn how many Vusers can run concurrently
--> Gives manual control over how many vusers can run and at what times
Goal Oriented Scenario:
--> Goal may be throughput, response time or number of concurrent Vusers
--> Loadrunner manages vusers automatically
Different Goal Oriented Scenarios are:
--> Virtual Users
--> Hits per second
--> Transaction per second
--> Transaction response time
--> Pages per minute
Q64. Why wouldn't you want to run virtual users on the same host as the loadrunner controller or database server?
Ans: Running virtual users on the same host as the loadrunner controller will skew the results so that they no longer emulate real life usage. By having both the controller and the vusers on the same machine, the tester will not be able to determine the effects of the network traffic
Q65. Each time you run the same scenario, the results will be slightly different. What are some factors that can cause differences in performance measurements?
Ans: Different factors can effect the performance measurements including network traffic, CPU usage and caching.
Q66. What are some of the reaons to use the server Resources Monitor?
Ans: (1) To find out how much data is coming from cache
(2) To help find out what parts of the system might contain bottlenecks
Q67. Explain the above:
Ans: Hits per second graph:
Hits per second graph shows the number of HTTP requests made by vusers to the web server during each second of the scenario run. This graph helps to evaluate the amount of load vusers generate, in terms of the number of hits
Pages download per second graph:
The Pages downloaded per second graph shows the number of web pages (y-axis) downloaded from the server during each second of the scenario run (x-axis). This graph helps to evaluate the amount of load vusers generate, in terms of the number of pages downloaded.
Transaction Response time (under load) graph:
The Transaction Response Time (under load) graph is a combination of the running vusers and average transaction reponse time graphs and indicates transaction times relative to the number of vusers running at any given point during the scenario. This graph helps to view general impact of vuser load on performance time and is most useful when analyzing a scenario with a gradual load.
Transaction Response Time (percentile) graph:
The transaction response time (Percentile) graph analyzes the percentage of transactions that were performed within a given time range. This graph helps to determine the percentage of transactions that met the performance criteria denfined in the system
Network delay time graph:
The network delay time graph shows the delays for the complete path between the source and destination machines (for example, the database server and vuser load generator).
Q1. What is Load Testing?
Ans: 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
Q2. What is Performance testing?
Ans: Timing for both read and update transactions should be gathered to determine whether system functions are being performed in an acceptable time frame. This should be done stand alone and then in a multi user environment to determine the effect of multiple transactions on the timing of a single transaction
Q3. Did you use Loarunner? What version?
Ans: Yes, 11.0
Q4. Explain the Load testing process.
Ans: Step 1: Planning the test
Here, we develop clearly defined test plan to ensure that test scenarios we create will accomplish load-testing objectives
Step 2: Creating Vusers
In this step Vuser scripts are created 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 build a scenario for us.
Step 4: Running the scenario
We emulate load on the server by instructing multiple Vusers to perform tasks simultaneoulsy. 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.
Q5. When do you do performance testing?
Ans: We perform load testing once we are done with interface (GUI) testing. Modern system architectures are large and complex. Where as 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 hundereds and thousands of users, etc. This is when we set do load and performance testing
Q6. What are the components of Loadrunner?
Ans: The components of Loadrunner are 1) The Virtual User (Vuser) Generator 2) Controller and 3) Analyzer
Q7. What component of Loadrunner would you use to record a script?
Ans: The Virtual User Generator (VuGen) component is used to record a script. It enables to develop Vuser scripts for a variety of application types and communication protocols
Q8. 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
Q9. What is rendezvous point?
Ans: Rendezvous point is inserted in the 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
Q10. What is a scenario?
Ans: 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.
Q11. 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 send to, and received from, the database server.
We use Vugen to:
a) Monitor the communication between the application and the server
b) Generate the required function calls and
c) Insert the generated function calls into a Vuser script
Q12. 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
Main reasons to create parameters are
a) Different sets of data are sent to the server each time the script is run
b) Better simulate the usage model for more accurate testing from the Controller; one script can emulate many different users on the system.
Q13. 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 correaltion 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.
Q14. How do you find out where correlation is required? Give few examples from your projects?
Ans: There are two ways to find correlation
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 insurance number, it was generated automatically and it was sequential and this was unique. I had to correlate this value, in order to avoid eroors while running my script. I did using scan for correlation
Q15. 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 message 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 need to create correlation for the value and specify how the value to be created.
Q16. What is a function to capture dynamic values in the web Vuser script?
Ans: web_reg_param function saves dynamic data information to a parameter
Q17. 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 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 send 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 warning 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 speicify which additional information should be added to the extended log using the Extended log options
Q18. How to 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.
Q19. How do you write user defined functions in Loadrunner? Give a few functions?
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 above format:
_declspec (dllexport) char* (char*, char*)
Examples of user defined functions are above:
Get Version, GetCurrentTime, GetPltform are some of the user defined functions are the examples
Q20. 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 Extended
c) 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
Q21. Where do you set Iteration for Vuser testing?
Ans: We set iterations in the run time settingd of the VuGen. The navigation for this is run time settings --> Pacing tab --> set number of iterations.
Q22. How to 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
Q23. What is Ramp up? How to set this?
Ans: This option is used to gradually increase the amount of Vusers/load on the sercer. An initial value is set and a value to wait between intervals can be specified. To set Ramp up, go to 'Scenario Scheduling Options'
Q24. What is the advantage of running the Vuser as thread?
Ans: VuGen provides the facility to use multi threading. 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.
Q25. If you want to stop the execution of the script on error, how do you do that?
Ans: 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.
Q26. What is the relation between Response time and Throughput?
Ans: Throughput graph shows the amount of data in bytes that the Vusers recived from the server in a second. When we compare this with the transaction reponse time, we will notice that as throughput decreased. Similarly the peak throughput and highest reponse time would occur approximately at the same time.
Q27. Explain the configuration of your system?
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.
Q28. How do you identify the performance bottlenecks?
Ans: Performacne Bottlenecks can be detected by using monitors. These monitors might be application server monitors, web server monitors, database server monitors and network moniotrs. They help in finding out the troubled area in our scenario which causes increased response time. The measurements made are usually performance reponse time, throughput, hits/sec, network delay graphs, etc.
Q29. 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.
Q30. How did you find web server realted issues?
Ans: Using web resource monitors we can find the performance of web servers. Using these monitors we can analyze thoroughput on the web server, number of hits per second that occured during scenario, the number of http reponses per second, the number of downloaded pages per second.
Q31. How id you find database releated issues?
Ans: By running "Database" monitor and help of "Data Resource Graph" we can find database related issues. For an example we can specify the resource you want to measure on before running the controller and then you can see database related issues
Q32. Explain all the web recording options.
Ans:
Q33. What is the difference between Overlay graph and Correlate graph?
Ans: Overlay Graph: It overlays 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 and 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 graph's y-axis
Q34. How do 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 two important documents. They are 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 inforamtion about the transactions name and their priority levels with regard to the scenario we are deciding.
Q35. What does vuser_init action contain?
Ans: Vuser_init action contains procedures to login to a server.
Q36. What does vuser_end action contain?
Ans: Vuser_end section contains log off procedures
Q37. What is think time? How can 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.
Q38. What is the difference between standard and extended log?
Ans: Standard log: It sends a subset of functions and messages send during script extended to a log. The subset depends on the Vuser type.
Extended log: It sends a detailed script execution messages to the output log. This mainly used during debugging when we want information about:
a) Parameter substitution
b) Data returned by the server
c) Advance trace
Q39. Explain the above functions:
Ans:
a) lr_debug_message
The lr_debug_message function sends a debug message to the output log when the specified message class is set
b) lr_output_message
The lr_output_message function sends notifications to the controller output window and the Vuser log file
c) lr_error_message
The lr_error_message function sends an error message to the loadrunner output window
d) 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
e) lrd_fetch
The lrd_fetch function fetches the next row from the result set
Q40. Explain about Throughput?
Ans: If the troughput 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.
Q41. What are the types of Goals in Goal-oriented Scenario?
Ans: Loadrunner provides with five differenet types of goals in a goal oriented scenario:
1) The number of concurrent Vusers
2) The number of hits per second
3) The number of transactions per second
4) The number of pages per minute
5) The transaction response time
Analysis Scenario (Bottlenecks):
In running Vuser graph correlated with the response time graph one 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 fifty six Vusers, there is a sudden, sharp increase in the average response time. We say that the test broke the server. That is mean time before failure (MTBF). The response time clearly began to degrade when there were more than fifty six Vusers running simultaneously
Q42. 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
Q43. What are the three sections of a Vuser script and what is the purpose of each one?
Ans: 1) Vuser_init - used for recording the logon
2) Actions - used for recording the business process
3) Vuser_end - used for recording the logoff
Q44. For what purpose are Vusers created?
Ans: Vusers are created to emulate real users acting on the server for the purpose of load testing
Q45. What are the beifits of multiple action files within a Vuser?
Ans: They allow to perform different business processes in one Vuser to represent a real user who does the ame thing. They let you build Vusers that emulate real users defined in the User Community profile. They also allow you to record the login and logoff separately from the Action files and thus to avoid iteration
Q46. How can you tell the difference between an integer value and a string value in a Vugen script?
Ans: Strings are enclosed in quotes; integers are not
Q47. What is the purpose of loadrunner transaction?
Ans: Loadrunner transaction is to measure one or more steps/user actions of a business process
Q48. What is the easiest way to get measurements for each step of a recorded script?
Ans: For entire action file? Enable automatic transactions (Runtime settings, Recording Options)
Q49. When would you parameterize a value rather than correlate queries?
Ans: Parameterize a value only when it is input by the user
Q50. What are the four selection methods when choosing data from a data file?
Ans: Sequential, Random, Unique and same line as
Q51. How can reusing the same data during iterative execution of a business process negatively affect load testing results?
Ans: In reusing the same data for each iteration, the server recognizes the same data is requested and places it in its cache. The load test then gets performance results that are not based on real server activity but caching. This will not provide the correct results during the analysis of the load test.
Q52. How can caching negatively affect load testing results?
Ans: When data is cached in the server's memory, the server does not need to fetch it from the database during playback. Then, test results do not reflect the same performance they would if real users were loading the system with different data
Q53. Why is it recommeneded to add verification checks to the Vusers?
Ans: If we want to verify, using loadrunner that the business process is functioning as expected under load
Q54. When does VuGen record a web_submit_data instead of a web_submit_form? Why? (Be as specific as possible)
Ans: A web_submit_data is recorded when Vugen cannot match the action, method, data fields, and/or hidden data values with the page that is stored in the record proxy cache. Comparison failures are typically caused by something other than HTML setting the properties of the HTTP request. Because VuGen can parse only HTML, it cannot find all the properties of the HTTP request in memory. This results in the hard coding of all the request information in a web_submit_data statement.
Q55. What do you need to do to be able to view parameter substitution in the execution log?
Ans: Check extended log and parameter substitution in the Run-time settings
Q56. How can you determine which field is data dependent?
Ans: Re-record the same script using different input values, and then compare the two scripts
Q57. Where should the rendezvous be placed in the script?
Ans: The rendezvous should be placed immediately before the transaction where you want to create peak load. In this case, the rendezvous should be placed right before starting the update order transaction
Q58. For what purpose should you select continue on error?
Ans: Set it only when making execution logs more descriptive or adding logic to the vuser
Q59. What is the purpose of selecting show browser during replay in the general options settings?
Ans: This setting allows to see the pages that appear during playback. This is useful for debugging Vuser during the initail stages of web Vuser creation
Q60. What tools does vugen provide to help to analyze vuser run results?
Ans: Execution Log, Run-Time Viewer and Mercury Test results window
Q61. If your Vuser script had two parameters, "DepartCity" and "Arrival City" how could you have the vuser script return an error message which included the city names?
Ans: lr_error_message ("The Vuser could not submit the reservation request for "%s to %s", (lr_eval_string("{DepartCity}"), lr_eval_string("{ArrivalCity}"));
Q62. Why should you run more Vusers than your anticipated peak load?
Ans: (1) To test the scalability of the system
(2) To see what happenes when there is a spike in system usage
Q63. What is the difference between manual scenario and Goal oriented scenario? How Goal oriented scenarios can be created?
Ans: Manual Scenario:
--> Main purpose is to learn how many Vusers can run concurrently
--> Gives manual control over how many vusers can run and at what times
Goal Oriented Scenario:
--> Goal may be throughput, response time or number of concurrent Vusers
--> Loadrunner manages vusers automatically
Different Goal Oriented Scenarios are:
--> Virtual Users
--> Hits per second
--> Transaction per second
--> Transaction response time
--> Pages per minute
Q64. Why wouldn't you want to run virtual users on the same host as the loadrunner controller or database server?
Ans: Running virtual users on the same host as the loadrunner controller will skew the results so that they no longer emulate real life usage. By having both the controller and the vusers on the same machine, the tester will not be able to determine the effects of the network traffic
Q65. Each time you run the same scenario, the results will be slightly different. What are some factors that can cause differences in performance measurements?
Ans: Different factors can effect the performance measurements including network traffic, CPU usage and caching.
Q66. What are some of the reaons to use the server Resources Monitor?
Ans: (1) To find out how much data is coming from cache
(2) To help find out what parts of the system might contain bottlenecks
Q67. Explain the above:
Ans: Hits per second graph:
Hits per second graph shows the number of HTTP requests made by vusers to the web server during each second of the scenario run. This graph helps to evaluate the amount of load vusers generate, in terms of the number of hits
Pages download per second graph:
The Pages downloaded per second graph shows the number of web pages (y-axis) downloaded from the server during each second of the scenario run (x-axis). This graph helps to evaluate the amount of load vusers generate, in terms of the number of pages downloaded.
Transaction Response time (under load) graph:
The Transaction Response Time (under load) graph is a combination of the running vusers and average transaction reponse time graphs and indicates transaction times relative to the number of vusers running at any given point during the scenario. This graph helps to view general impact of vuser load on performance time and is most useful when analyzing a scenario with a gradual load.
Transaction Response Time (percentile) graph:
The transaction response time (Percentile) graph analyzes the percentage of transactions that were performed within a given time range. This graph helps to determine the percentage of transactions that met the performance criteria denfined in the system
Network delay time graph:
The network delay time graph shows the delays for the complete path between the source and destination machines (for example, the database server and vuser load generator).
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