Thursday, 1 March 2012

Loadrunner Interview Questions - Part III

Loadrunner Interview Questions - Part III

25. How many types of graphs are available in LoadRunner and what are they?
There are 5 types of graphs:
Network delay time graph – displays the time the elapses between request and response
Two transaction response time graphs – one for load and one for percentile
Hits/second graph – Shows application traffic volume.
Pages download/second graph – shows the rate that download processes are performed

26.. How can performance bottlenecks be identified?
LoadRunner has monitors that can be used to detect performance bottlenecks. These include network, web server, application server, and database server monitors. These monitors can be used to locate trouble spots in scenarios that cause increases response time and they track throughput, network delays, performance response time, hits/sec, etc.

27. How can one tell when correlation can be performed?
There are two ways to do this. One is to use the scan function to search for correlations and select a value from the resulting list. The second is to record a pair of scripts and then compare them to each other.

28. Where are automatic correlation options set?
The automatic correlation is set in recording options area on the correlation tab. From here, correlation can be enabled for the full script and rules for correlation can be defined.   Automatic correlation can be performed on a database by viewing the output window, scanning for correlation, and selecting the value that will be used.

29. Where is the number of iterations set for testing with Vuser scripts?
The number of iterations is set in the VuGen pacing tab in the Run-time settings area.

30. What is ramp up and how can it be set?
Ramp up is gradually increasing the load on a server.  This is simulated by gradually increasing the number of Vusers.  This feature can be found in the Scenario Scheduling Options.  When used, the initial value and the time to wait between periods are specified.

31. What is the benefit of running a Vuser script as a thread?
The advantage of running a Vuser script as a thread is that it allows more Vusers to be used for one load generator. Running Vuser scripts as processes utilizes a lot of memory because all of the loaded scripts use the same driver.  This limits the number of Vuser scripts that can be run on one generator.

32. How do you set LoadRunner to stop script execution when an error occurs?
Execution of Vuser scripts can be stopped on error using LoadRunner’s lr_abort function. The “Continue on error” option must not be checked in the Run-Time Setting menu.  It is helpful when it is necessary to abort execution when a certain error condition occurs. This function instructs the Vuser to stop performing what is in the Actions section, and to begin performing the vuser_end functions.  When execution is terminated, the Vuser status is changed to “Stopped”.

33. How are throughput and response time related?
The graph for throughput displays the quantity of data that the server sent to the Vusers in one second. When throughput is compared to the response time of transaction, it decreased as the response time decreased. In addition to this, the highest throughput and response times occur at approximately the same time.

34. Define think time and explain how you change the threshold for it.
Think time is the interval of time that a user must wait between actions. An example of this is the time that a user takes to review data after receiving it from the server before responding to it.  The threshold is the maximum level at which this time will be ignored.  The default threshold value is five seconds but this can be modified in the VuGen Recording options.

35. Explain the difference between standard and extended log?
The standard log contains a subset of functions and messages, which vary based on the type of Vuser, which are generated during the execution of a script. The extended log creates a more detailed listing of functions and messages.

Loadrunner Interview Questions

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  1. When Throughput increases Response time decreases