# Performance testing - usage example

> **VU units** are pulled from the license server at runtime and released back to the license pool after your performance tests are finished. The execution of performance tests will be allowed by the system if there are sufficient unused **VU units** on the license server. The execution of performance tests will be blocked by the system if there aren’t sufficient **VU units** available on the license server.

**VU units** are pulled from the license server at runtime and released back to the license pool after your performance tests are finished. The execution of performance tests will be allowed by the system if there are sufficient unused **VU units** on the license server. The execution of performance tests will be blocked by the system if there aren’t sufficient **VU units** available on the license server.

## Example 1 - Execution of performance tests is allowed

In the following example, a customer who owns 1 bundle (2,500 **VU units**) creates 2 testing scenarios.

* **Test Scenario 1**
  + 1 Web UI test case with 100 virtual users = 1,000 **VU units**
  + 1 API test case with 500 virtual users = 500 **VU units**
  + **Total:** 1,500 **VU units**

* **Test Scenario 2**
  + 1 Desktop test case with 10 virtual users = 1,000 **VU units**
  + **Total:** 1,000 **VU units**

Combined, the 2 testing scenarios can be executed within the provisioned license limit.

**Scenario 1 + Scenario 2 = 2,500 VU units**

## Example 2 - Execution of performance tests is blocked

In the following example, a customer who owns 1 bundle (2,500 **VU units**) creates 2 testing scenarios.

* **Test Scenario 1**
  + 1 Web UI test case with 100 virtual users = 1,000 **VU units**
  + 1 API test case with 500 virtual users = 500 **VU units**
  + **Total:** 1,500 **VU units**

* **Test Scenario 2**
  + 15 Desktop test cases with 10 virtual users = 1,500 **VU units**
  + **Total:** 1,500 **VU units**

Combined, the 2 testing scenarios exceed the provisioned license limit. For this example, only **Test Scenario 1** is run. However, when **Test Scenario 1** (or another test worth at least 1,500 **VU units**) is completed, users can trigger the execution of **Test Scenario 2**. After a scenario execution completes, the used **VU units** are released back to the license server and they become available again. Users can, at this point, run the scenarios that may have previously exceeded the available **VU unit** capacity.

**Scenario 1 + Scenario 2 = 3,000 VU units**