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Basics: Transaction Response TIme

What is Transaction Response Time?

Transaction Response Time represents the time taken for the application to complete a defined transaction or business process.

Why is important to measure Transaction Response Time?

The objective of a performance test is to ensure that the application is working perfectly under load. However, the definition of “perfectly” under load may vary with different systems.
By defining an initial acceptable response time, we can benchmark the application if it is performing as anticipated.

The importance of Transaction Response Time is that it gives the project team/ application team an idea of how the application is performing in the measurement of time. With this information, they can relate to the users/customers on the expected time when processing request or understanding how their application performed.

What does Transaction Response Time encompass?

The Transaction Response Time encompasses the time taken for the request made to the web server, there after being process by the Web Server and sent to the Application Server. Which in most instances will make a request to the Database Server. All this will then be repeated again backward from the Database Server, Application Server, Web Server and back to the user. Take note that the time taken for the request or data in the network transmission is also factored in.

To simplify, the Transaction Response Time comprises of the following:
  1. Processing time on Web Server
  2. Processing time on Application Server
  3. Processing time on Database Server
  4. Network latency between the servers, and the client
The following diagram illustrates Transaction Response Time.

Figure 1 Transaction Response Time = (t1 + t2 + t3 + t4 + t5 + t6 + t7 + t8 + t9) X 2
Factoring the time taken for the data to return to the client.

How do we measure?

Measuring of the Transaction Response Time begins when the defined transaction makes a request to the application. From here, till the transaction completes before proceeding with the next subsequent request (in terms of transaction), the time is been measured and will stop when the transaction completes.

Differences with Hits Per Seconds

Hits per Seconds measures the number of “hits” made to a web server. These “hits” could be a request made to the web server for data or graphics. However, this counter does not represent well to users on how well their applications is performing as it measures the number of times the web server is being accessed.

How can we use Transaction Response Time to analyze performance issue?

Transaction Response Time allows us to identify abnormalities when performance issues surface. This will be represented as slow response of the transaction, which differs significantly (or slightly) from the average of the Transaction Response Time.

With this, we can further drill down by correlation using other measurements such as the number of virtual users that is accessing the application at the point of time and the system-related metrics (e.g. CPU Utilization) to identify the root cause.

Bringing all the data that have been collected during the load test, we can correlate the measurements to find trends and bottlenecks between the response time, the amount of load that was generated and the payload of all the components of the application.

How is it beneficial to the Project Team?

Using Transaction Response Time, Project Team can better relate to their users using transactions as a form of language protocol that their users can comprehend. Users will be able to know that transactions (or business processes) are performing at an acceptable level in terms of time.

Users may be unable to understand the meaning of CPU utilization or Memory usage and thus using a common language of time is ideal to convey performance-related issues.

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1 Responses to “Basics: Transaction Response TIme”

  1. # Anonymous Dinesh

    Good Post.Any idea how can I check Time taken by webserver to process say 100 requests made at same point of time using loadrunner.  

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