45个LoadRunner 面试问题(附答案)英文(3)

　　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.

　　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.

　　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 be

　　specified. To set Ramp Up, go to ‘Scenario Scheduling Options’

　　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.

　　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.

　　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.

　　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.

　　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.

　　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.

　　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.

　　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

　　Explain all the web recording options?

　　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.

　　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.

原文转自：http://www.ltesting.net