The methods for controlling the number of concurrently executing threads include the controlling in Web container, in Web application, and in URL group.

• Controlling the number of concurrently executing threads in a Web container
  Set the number of threads for processing the requests concurrently in all Web applications on a Web container. For details, see 2.16 Controlling the number of concurrently executing threads in the Web container.
  
• Controlling the number of concurrently executing threads in a Web application
  Set the number of threads for processing the requests concurrently in each Web application on a Web container. You can control the number of threads more carefully as compared to the method for controlling the number of concurrently executing threads in Web container. For details, see 2.17 Controlling the number of concurrently executing threads in the Web application.
  
• Controlling the number of concurrently executing threads in a URL group
  Set the number of threads for processing the requests concurrently in URL corresponding to business logic, such as servlet and JavaBeans, in a Web application. A business logic that processes the requests sent to a specific URL is called a URL group. Since the number of concurrently executing threads is controlled in URL group, you can control the number of threads more carefully as compared to the method for controlling in Web application. For details, see 2.18 Controlling the number of concurrently executing threads in the URL group.
  

The following figure shows the relationship between each control unit:

Figure 2-16 Relationship between each control unit of the number of concurrently executing threads

As shown in the figure, the biggest unit of controlling the number of concurrently executing threads is the Web container. In the case of controlling the number of threads in each Web application of the Web container, specify the control in the Web application. In the case of controlling the number of threads in URL group of a Web application, specify the control in the URL group. The smallest unit of controlling the number of threads is the URL group.

Controlling the number of threads has an inclusion relation, and hence, in the case of controlling the number of threads in the Web application, you also need to specify the setting in the Web container. Moreover, in the case you control the number of threads in the URL group, you also need to specify the setting in the Web container and the Web application.