Setting rate load

By setting stages, you can model workloads over time and change the number of transactions that perform certain tasks to reflect real-world usage. You can divide the load into stages and collect performance metrics for each stage independently, which means that a single run can more efficiently accomplish the work of multiple runs. Each stage, which lasts a specific amount of time and contains a specific number of transactions, defines a different load. Each load is used to derive a certain rate of transactions in a given time.

You can add load only to the Rate Schedule Details section. When you add the load, they are automatically displayed in the Rate Runner Group Details section. Managing the rate at which the load is to be run is specified in the Rate Runner Group Details section. You can change the rate at the time of the run too.

  1. In the Test Navigator, browse to the rate schedule and double-click it. In the Rate Schedule editor that opens, the Load category displays one stage that runs for 10 minutes.
  2. In Rate Schedule Details section, click Add.
  3. Specify the duration of the stage and the settle time. The time required for the system to stabilize in between reaching the peak load and starting another stage is called settle time.
  4. Click OK.
    The new stage is added to the Rate Schedule and is displayed to all the Rate Runner Groups.
  5. In Time limit to respond to a stop request, specify a duration value.
    If a stage contains fewer iterations than its predecessor, the excess iterations in the previous stage are asked to stop. This duration value gives a stopped iteration extra time to complete its current action (such as an HTTP request). If the iteration cannot complete its action before the time limit expires, it is forced to stop. Note that a long time limit might delay the next stage.
  6. Optional: To update the stage details, click a Rate Runner Group, select a stage from the table, and click the Show Advanced check box. You can also click the Edit button and update the following options.
    Iteration rate
    Specify the rate at which a transaction needs to be executed.
    Distribution
    Specify the frequency rate at which the rate generator should run.
    Constant: The workload of the rate generator occurs exactly at the rate you specify. For example, if the iteration rate is 4 per minute, the workload starts at 15 seconds, 30 seconds, 45 seconds, and 60 seconds, which is exactly 4 every minute, evenly spaced, with a 15-second interval.
    Uniform: The time between each workload is not constant. However, the workload that occurred over time averages out to the rate that you specified. The time between the start of each workload is chosen randomly with a uniform distribution within the selected range.
    Negative Exponential: This type of distribution emulates the spike of activity followed by a lean period that is typical of user behavior. Therefore, if the rate is 4 every minute, the probability that the workload starts immediately is high but decreases over time. Test Performance maintains the desired average rate.
    Change Rate
    Use this option to ramp up or ramp down the iteration rate to the desired level.
    Min Clients
    Specify the minimum number of clients to be used to achieve the desired rate of execution. This option is typically used by an advanced user if the default number of clients do not meet the desired rate.
    Max Clients
    Specify the maximum number of clients to be used to achieve the desired rate of execution.
  7. Save the Rate Schedule.