Performance Testing, LoadRunner Tips and Tricks

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Content Page - General
2007-05-09 11:38:00
GeneralGeneral: How does LoadRunner license work? General: Are client activities recorded by Vugen? General: Scenario Execution General: Detecting Memory Leaks Using LoadRunnerUnderstanding MemoryPage Fault Resolution Performance Concerns Virtual Memory Shortage AlertsAvailable Bytes LRU System Working Set Detecting Memory LeaksMeasuring Memory Utilization
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Content Page - Scripts
2007-05-09 11:25:00
Scripts: Duplicating Files on the Fly Scripts: Step Download Timeout Scripts: VIEWSTATE Scripts: Auto or Manual Correlation?Scripts: Remove Think Time Scripts: Set Debug Mode in ScriptScripts: Replay Failure – Use Full Extended Log!
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Content Page - Monitors
2007-05-09 11:20:00
Monitors: How does the monitoring work? Monitors: What metrics/counters to monitor for Windows System Resource? Monitors: The Other Way?Monitors: Unix System ResourceMonitors: MS SQL Server
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Content Page - Protocols
2007-05-09 10:30:00
GeneralWhat Prot ocol to Use?Web (HTTP/HTML)Working with Web (HTTP/HTML) Working with Web (HTTP/HTML) II - Differences in WinINet and Socket Working with Web (HTTP/HTML) III - NTLM AuthenticationWorking with Web (HTTP/HTML) IV - Internet Explorer 7 SupportJavaWorking with RMI-Java Working with Java - Introduction CitrixWorking with CitrixWorking with Citrix II - Best Practices by LoadTesterWinsockWorking with Winsock by LoadTester
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General: Detecting Memory Leaks Using LoadRunner
2007-05-08 04:50:00
How to effectively use Load Runner to detect memory leaks? First, I recommend you to read the article “Detecting Memory Leaks” that I’ve extracted from the “Windows 2000 Performance Guide by Mark Friedman & Odysseas Pentakalos” to understand the definition of memory leak.Here, as we discussed memory leak, we are referring the memory leakage on the server side NOT the client side. Therefore, if you are searching for information on client-side application memory leakage, you can try the SQA Forums which may provide more relevant information to you.With the mentioned materials, we can use the Available Bytes, Committed Bytes and the number of Running Vusers to determine if memory leakage occurred.Setup the scenario with Available Bytes and Committed Bytes as one of the counters to monitor. Run the load test as per norm. Observe the pattern of memory usage on the designated server with the ramp up of Vusers and see if they correlate.When the memory usage peaks at a ceiling,...
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General: Understanding Memory - Measuring Memory Utilization
2007-05-06 17:28:00
Available Bytes is an instantaneous counter that measures real memory allocation, and is the single most important measure of memory utilization available in Windows. The Available Bytes counter reports the current size of the Standby, Free, and Zero lists. The Standby list contains pages recently trimmed from executing process working sets. New pages that processes requests are created from the Zero list of aged pages, or, if the Zero list is empty, from the Free list. The current number of Available Bytes is fundamentally a measure of memory occupancy. By implication, it reports on how much RAM is currently free: Real memory allocated = Size of RAM – Available Bytes However, as discussed previously, this is not always a safe assumption in Windows because there are some anomalies in the way memory allocations are accounted for. A good configuration rule of thumb is to maintain a buffer of Available Bytes equal to approximately 5 – 10% of total RAM. Maintaining an ample supply o...
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General: Understanding Memory - Detecting Memory Leaks
2007-05-06 17:28:00
Memory leaks are caused by programs that allocate virtual memory, fail to free after they are finished with it. Memory leaks are nasty program bugs that are sometimes difficult to find. A program containing memory leak bug often executes to completion and produces the correct results, so the presence of the bug is not always detected. In fact, as long as the program containing the memory leak does not impact other executing processes, the bug can go undetected for a long time. The telltale sign of a memory leak is that Committed Bytes at the system level and/or Virtual Bytes at the process level are continuously increasing. Eventually, a program with a memory leak exhausts the system’s supply of virtual memory, which can cause other running programs and even system code to fail as the system runs up against the virtual memory Committed Bytes limit. Depending on the rate at which the defective program leaks memory and the amount of excess virtual memory available, it can be a long ...
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General: Understanding Memory - System Working Set
2007-05-06 17:22:00
Windows OS functions also consumes RAM, so the system has a working set that needs to be controlled and managed like any other process. In this section we discuss the components of the system working set and look at how it is managed. Both system code and device driver code occupies memory. In addition, the OS allocates data structures in two areas of memory: a pool for non-pageable storage and a pool for pageable storage. Data structures accessed by OS and driver functions when interrupts are disabled must be resident in RAM at the time they are referenced. These data structure are usually allocated from the non-pageable pool so that they reside permanently in RAM. The Pool Nonpages Bytes counter in the Memory object shows the amount of RAM currently allocated that is permanently resident in RAM. Mainly, though, most system data structure are pageable: they are created in a pageable pool of storage and subject to page replacement like the virtual memory pages of any other process. ...
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Scripts: Step Download Timeout
2007-05-06 17:19:00
Step Download Timeout means that the step needed to performed for the subsequent step to be performed have reached its timeout limit (default is 120 secs) in Load Runner. A more detailed explanation can be found in KB 15370 .Having mentioned the above, there are situations we must take note when this error occur. If the error occurs during the generation of the script (replay in Vugen), it could mean that the application is really taking time of more than 120 secs to complete the download of the resources. You may want to configure the timing to suit your application needs.If the error occurs during a scenario execution and happens in the middle of the scenario (usually with a large amount of load), the application is handling alot of load and unable to attend to all the vuser request, thus (maybe) taking more than the configured download timing. For this, it will be better advisable to look at the system utilization of the servers to seeth out any performance problems.To determine t...
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General: Understanding Processor
2007-05-04 16:52:00
Windows is a multiprogramming OS, which means that it manages and selects among multiple programs that can all be active in various stages of execution at the same time. The displaceable unit in Windows, representing the application or system code to be executed, is the thread. The Scheduler running inside the Windows OS kernel keeps track of each thread in the system and points the processor hardware to threads that are ready to run.The basic rationale for multiprogramming is that most computing tasks do not execute instructions continuously. After a program thread executes for some period of time, it usually needs to perform an I/O operation like reading information from the disk, printing characters on a printer, or drawing data on the display. While the program is waiting for this I/O function to complete, it does not need to hand on to the processor. An OS that supports multiprogramming saves the status of a program that is waiting, restores its status when it is ready to resum...
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