Monitoring and Tuning Your Server

Process Throttling

Process throttling limits the CPU usage of out-of-process applications and CGI applications on a per-site basis. The allowed amount is a percentage of the total CPU usage during a given interval, which defaults to one day.

There are four actions that can be taken when a limit is exceeded:

The lowest level action, engaged whenever a limited site exceeds its allocation at all, is that IIS 5.0 logs the error.
The second level action, engaged when the site exceeds 150 percent of its allocation, is that all out-of-process applications on the site have their CPU priority set to idle.
The next-to-highest level action, engaged when the site exceeds 200 percent of its allocation, is that IIS 5.0 halts all processes on the site that are affected by throttling, such as all CGI applications and out-of-process applications. These must then be restarted.
The highest level action is accessible only through the CPULimitPause property of the metabase. When this level is triggered, IIS 5.0 pauses the entire site and causes the server to issue a custom error message when any client attempts to connect to that site. (See the IIS 5.0 online product documentation for more information about this and other metabase settings.)

Process throttling also limits CGI processes to a certain amount of CPU usage. If your server performs CGI processing, you should probably lower the CGI timeout interval. For more information, see the IIS 5.0 online product documentation for more information. If you support a large number of long-running CGI applications, see A Thread-Related CGI Program Issue.