You create categories and custom performance counters if you want to track data that is not captured by the standard counters provided with Microsoft Windows. For example, you might create a custom counter to track the total number of orders processed by your Web site, or to track the orders processed per second by your site. When you create a counter, you add it to a performance counter category, and you assign it a type that governs how it will behave. For information on choosing the correct type, see Performance Counter Types.
There are several ways you can create custom counters:
You must create counters in a user-defined category rather than in the performance objects (called categories) defined by Windows. That is, you cannot create a new counter within the Processor category or any other non-user-defined categories. Additionally, you must create a counter in a new category; adding a counter to an existing user-defined category will overwrite all of the counters that category already contains.
The following restrictions apply to the process of creating new counters:
Caution This restriction includes counter categories you have created yourself. You can create a new counter in a user-defined category, but it will replace the existing counters within that category.
Creating Custom Performance Counters | Creating Performance Counter Categories | Deleting Performance Counter Categories | Determining if Counters and Categories Exist | Removing Performance Counter Instances | Performance Counter Types