Performance goal be in terms of concurrent users?

We often come across such kind of questions like how many users would require for performance testing.

We can use two approach:--

1. First Approach:

Assume that we have  5000 average visitors per day and working window is 12 hours

So calculate like this ....

Average visits per hour = (5000 average visitors/day) / 12 hours = 417

Average Concurrent Users = Visits per hour / (60 min/hour / average visit.

2. Second Approach 

This approach is going to tell us how many users we have on average. 

U = V / (60/D)

Where:

U is the number of load test virtual users (that's what we are trying to figure out)

V is the average number of visitors per hour

D is the average duration of a visitor

60 is the number of minutes in an hour

Also , we can use

                                   Users = Pages views per hours * Avg. duration of script execution

                                                                   60  * Total No. of pages in the script

what is 95th percentile report

Lets assume , You have recorded script and executed the same for 100 transaction

Suppose you have SLA( client's requirement)
----> 95% of transaction Execution Response time = 5 seconds.

Now, you can verify the same in percentile report what is the response time for 95th Percentile.....whether you have achieved the target or not.

Ex.  U have one transaction say "Login" and open 95% percentile report. Lets say response time =5 sec

We can say 95% execution of "Login" has been completed =< 5 seconds ( max =5 or beneath 5)

RPT Troubleshooting help

Problem:-> Test run aborted

 

 

Execution failure. No status received from location computername in interval seconds.

Explanation

The workbench has lost communication with one or more agent computers.

System action

The test run stops.

Solution :->

For each agent computer:

• Check that the playback Java process is running. If it is still running, the problem might be on the workbench computer where RPT is installed. Stop the Java process and all related typeperf and vmstat processes.
• Examine the problem determination log for error messages or exception messages.
• If the playback Java process is not running, search for javacore.* files. The contents of these files might help you determine the cause of the problem.
• Run tests again and monitor the memory size of the playback Java process. If the playback Java process is consistently running at its maximum heap size, the process might not have enough memory.

If the problem is not on an agent computer, check that the workbench computer has sufficient memory. To increase the available memory, either increase the workbench heap size or reduce the level and amount of execution history.

How to increase memory allocation for a localhost location

 

Problem

It is possible to see an error like:

Test Run aborted due to error

The Driver: <HOST_NAME> has become unresponsive, possibly due to an out-of-memory condition.

At last notification this driver was using 90+ percent of its allocated memory.

Please refer to the "Increasing memory allocation" Help topic for more information on how to increase memory allocation.

during playback of a Rational(R) Performance Tester (RPT) Test with many virtual users running on the test controller machine.

 

Cause

There are actually two heap sizes that RPT utilizes. The first one is the workbench heap, which is related to space available for controlling and monitoring the playback and reviewing results.

The second is the playback heap used by the virtual testers. This is the heap size you need to change to avoid out-of-memory conditions. When you're running the virtual testers on the same system as the workbench, there are several steps necessary to change this heap.

 

 

Solution :->

 

First you will need to create an "Agent" on the local host:

1) Decide upon a place to store the Deployment Location (either the project's root directory or a folder in the project under Test Navigator)

2) Right click at the folder from step 1 and select New and Other, then browse to Test Elements -> Location.

3) Name the Location Local and press Next and then Finish.

4) In the General Information section of the Local Location, make sure that 'Host name' is "localhost"

Problem:-> Test run aborted due to error

 

Virtual users have exited prior to stage completion.

Explanation

In a schedule with multiple stages, at the end of a stage that is configured with n virtual users, there were fewer than n virtual users running. The schedule did not assign enough work to the virtual users to keep them active for the duration of the stage, or the virtual users stopped because of an a different error. The workload problem can occur if you use multiple stages but do not enclose the workload in an infinite loop.

System action

The test run stops.

Solution :->

On the workbench computer, examine the workload for each user group in the schedule. Check that the entire workload is inside an infinite loop, so that the virtual users always remain active regardless of the stage duration.

If the tests already use infinite loops, then the agent computers might have encountered errors while running tests. To determine why virtual users stopped before the stage completed:

• Examine the test log for error or exception messages.
• Increase the test log level and decrease the number of users. Try running the schedule again. Examine the test log for error or exception messages.
• Simplify the workload by running one user in one stage. Check to see whether the single user takes the expected amount of time to complete all actions. If not, examine the test log and problem determination log for error or exception messages.

 

 

Problem:-> No local agent controller

 

 

Local computer is not running the Agent Controller.

Explanation

The agent controller coordinates schedule playback between the workbench and agent computers. The agent controller is not running on the local computer.

System action

No tests run.

Solution :->

Make sure that the agent controller is installed and running on the workbench computer. On Windows computers, the agent controller is a process called ACWinService. On Linux computers, the agent controller is a process called RAServer.

To start the agent controller, do one of the following steps:

1.  At a command prompt, change to the directory AgentController\bin in the product installation directory.

Start->run then type cmd

>cd “C:\Program Files\IBM\SDP70Shared\AgentController\bin”

Then Type

net start "IBM Rational Agent Controller"

• On Linux, change to the directory AgentController/bin in the product installation directory; then enter this command:

./RAStart.sh

 

 

 

 

 

Problem:-> Connection refused

 

Connection refused on host computername

Explanation

The agent controller can be configured to restrict playback to the local computer only. If the agent controller on an agent computer is configured for local playback only, it will not accept connections from other agent controllers.

System action

The test run stops.

Solution :->

Make sure that the agent controller is configured correctly.

To configure the agent controller on Windows:

2.  At a command prompt, change to the directory AgentController\bin in the product installation directory.

Start->run then type cmd

>cd “C:\Program Files\IBM\SDP70Shared\AgentController\bin”

3.  Type net stop "IBM Rational Agent Controller" to stop the agent controller.

4.  Type SetConfig.bat to run the configuration utility.

5.  

6.  Type net start "IBM Rational Agent Controller" to start the agent controller.

To configure the agent controller on Linux:

1.  At a command prompt, change to the directory AgentController/bin in the product installation directory.

2.  Type ./RAStop.sh to stop the agent controller.

3.  Type ./SetConfig.sh to run the configuration utility.

4.  Accept all of the default values except for network access mode. Set network access mode to ALL.

5.  Type ./RAStart.sh to start the agent controller.

Problem:-> Unable to connect to license server

When you get this error,

Solution :->

1) Check if "FLEXlm License Manager" service is running in Services [Control Panel>Administrator>Services: WinXP/Win2000].

Or

Start->run then type services.msc press <Enter>

Restart this service "FLEXlm License Manager"

2) Launch Rational License Administrator and check if all the floating licenses are served properly [Menu Item: Setting >Client Server Config >check if Use License Server Option is checked. Check if correct server name is entered and then click on show licenses]

3) Check if Installation manager is configured for the same server.

Once above steps are verified, launch RPT go to help>license Status and check the expiration date [Should be same as seen in license server] and then run you're schedule.

Problem:-> Start recording aborted, The Agent Controller on localhost: 10002 is unavailable

Symptom

When you start a recording in RPT, the following error message can occur:

Start recording aborted.

Reason:

IWAT3034E The Agent Controller on localhost:10002 is unavailable.

IWAT3035E Confirm the Agent Controller is still running, and verify the location in Window > Preferences > Test.

Solution :->

This problem typically indicates that the installation of the Remote Agent Controller (RAC) is not correct. If it is and if the IBM_Agent_Controller directory is present, RAC does not start because of other issues. The following suggestions could help to overcome the problem:

• Check the IBM Rational Agent Controller service.
  In the Tab Log on, it should read:
• Local System Account
• Allow service to interact with desktop

• Check RPT Windows > Preferences > Test.
• The Agent Controller local port should be 10002.

• Check the serviceconfig.xml file

Path :-> C:\Program Files\IBM\SDP70Shared\AgentController\config

Open the serviceconfig.xml and verify the followings

• Make sure that the Agent Controller uses port 10002
• One of these two lines must exist:

<Allow host="LOCAL"/>

or alternatively

<Allow host="ALL"/>

• Check the C:\Windows\System32\drivers\etc\host file.
• Make sure it contains the exact line:127.0.0.1 localhost
• Bring up RPT

Windows > Preferences > Profile and Logging > Hosts.

• Select the localhost: 10002 selections in the Default Hosts list.
• Click the Test Connection button.

• Open a command prompt,

• Run the command

netstat -a -o

• Look for a line like:
  TCP hostname:10002 hostname:0 LISTENING 3528.

Hostname is the actual name of the computer. The right-most value in this line (3528 above) should match the process ID (PID) for the RAService.exe process.

• From a command prompt, run the command

telnet localhost 10002

Note any error message that appears.

Make sure, that no firewall or other security application prevents it to start.

IP Spoofing in LR

When you run a scenario, the Vusers on each host machine use the host’s IP address. You can define multiple IP addresses on a host machine to emulate a real- life situation where users sit on different machines. When testing using Web protocols, by default Vusers on each host machine use the host's (agent's) IP address. Since a particular server keeps serving a specific IP address, load tests would reflect network router caching and other optimizations rather than the real-life situation where different users arrive to the server with different IP addresses. This is especially needed when the hardware configuration under test balances load across a "farm" of several (web or database) servers.  "IP spoofing" enables each host machine to "spoof" the server into thinking it is using many different IP addresses. The IP Wizard program (ipwizard.exe in LR bin) is used to define multiple IP addresses on each load generator host. However, the hosts must use static IP addresses rather than DHCP to dynamically assign addresses. Note: IP addresses include two components, a netid and hostid. The submask determines where the netid portion of the address stops and where the hostid begins. When a host machine is re-started, routing tables are updated with the new addresses. The IP Wizard program creates a batch file (nt_routing.bat for Windows and unix_routing.bat for UNIX machines) and .ips file which updates IP tables. To enable multiple IP Addressing At the LoadRunner Controller, pull down menu item Scenario, check "Enable IP Spoofer" . This enables "Multiple IP address mode" in the Options dialog General tab, which appears after "Expert mode" is checked on the Tools drop-down menu. IP allocation should be consistent with the way users are running. If users are running as a process then the IP allocation should be done as a process, and if users are running as a thread then IP allocation should be done as a thread After turning IP spoofing on or off, for the setting to take effect, the Load Generator needs to be disconnected and reconnected again. Application servers and network devices use IP addresses to identify clients. The application server often caches information about clients coming from the same machine. Network routers try to cache source and destination information to optimize throughput. If many users have the same IP address, both the server and the routers try to optimize. Since Vusers on the same host machine have the same IP address, server and router optimizations do not reflect real- life situations. LoadRunner’s multiple IP address feature enables Vusers running on a single machine to be identified by many IP addresses. The server and router recognize the Vusers as coming from different machines and as a result, the testing environment is more realistic. Adding IP Addresses to a Host LoadRunner includes an IP Wizard program that you run on each host machine to create multiple IP addresses. You add new IP addresses to a machine once and use the addresses for all scenarios. The following procedure summarizes how to add new IP addresses to a host: 1 Run the IP Wizard on the host machine to add a specified number of IP addresses. 2 Re- start the host machine. 3 Update the server’s routing table with the new addresses, if necessary. 4 Enable this feature from the Controller. Refer to see Enabling Multiple IP Addressing from the Controller Using the IP Wizard: The IP Wizard resides on each host machine. You run this process one time to create and save new IP addresses. The new addresses can be a range of addresses defined by the Internet Assignment Numbers Authority. They are for internal use only, and cannot connect to the internet. This range of addresses are the default used by the IP Wizard. To add new IP addresses to a host machine: 1 Invoke the IP Wizard from the LoadRunner program group. 2 If you have an existing file with IP address settings, select Load settings from file and choose the file. 3 If you are defining new settings, select New Settings . 4 Click Next to proceed to the next step. If you have more than one network card,choose the card to use for IP addresses and click Next .The optional Web server IP address step enables the IP Wizard to check the server’s routing table to see if it requires updating after the new IP addresses are added to the host. 5 To check the server’s routing table directly after adding the addresses, enter the server IP address.  6 Click Next to see a list of the machine’s IP address(es). Click Add to define the range of addresses.  IP addresses include two components, a netid and hostid. The submask determines where the netid portion of the address stops and where the hostid begins. 7 Select a class that represents the correct submask for the machine’s IP addresses.8Specify the number of addresses to create. Select Verify that  new IP addresses are not already in use to instruct the IP Wizard to check the new addresses. If some addresses are in use, the IP Wizard will only add the addresses not in use. 9 Click OK to proceed. After the IP Wizard creates the new addresses, the summary dialog box lists all of the IP addresses. 10 Click Finish to exit the IP Wizard. The IP Wizard Summary dialog box is dispalyed.

LR Controller online Graphs Directory to modify

1. By default, the Controller online monitor shows a maximum of 20 measurements for each graph. To increase it, go to the LoadRunner\dat\online_graphs directory to modify the value ofMaxDispMeasurments= in the file controlling each type of graph:

Description	File Name
All	generalsettings.ini
System Resource Graphs	online_resource_graphs.rmd
Runtime Graphs	online_runtime_graphs.def
Transaction Graphs	online_transaction_graphs.def
Web Resource Graphs	online_web_graphs.def
Streaming Media	online_web_graphs_mms.def

2. Default counters for the System Resource, Microsoft IIS, Microsoft ASP, or SQL Server monitors are defined in the res_mon.dft file within the LoadRunner/dat folder. Its values can be pasted from the [MonItemPlus] section within scenario .lrs files.

LoadRunner interview questions

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. (Tell LR Version you worked on).
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 fromweb 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 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.
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* <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.
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 be
    specified. 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