URI Cache

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Applies To: Windows Server 2003, Windows Server 2003 with SP1

The user-mode URI cache is known as the URI cache. The URI cache stores metadata about a URL. Metadata can include a variety of configuration data, including data about headers and authentication. This configuration data is stored in the IIS Admin service. The URI cache stores the metadata as an object. For each request that reaches IIS user mode, the worker process checks the URI cache to see if the object for the requested URL has been cached. If the object has not been cached, the worker process must call the IIS Admin service for the appropriate metadata. This call is expensive from a performance and scalability standpoint. If the URI cache has a stored object for the URL, the request pulls in the object and continues processing.

The IIS Admin service is responsible for URI cache change notification. If, for example, Default.htm changes, the IIS Admin service tells the worker process to flush the URI cache for that specific URL. Subsequent requests for that URL are cached in the URI cache. Table 7.3 describes the preferred or ideal values for URI cache counters. For more information about IIS 6.0 counters, see the Performance Counters Reference.

Table 7.3 Preferred Values for URI Cache Counters

Object\Counter Preferred or Ideal Value

Web Service Cache\URI Cache Hits

Depends on content. If content cannot be cached in the HTTP.sys response cache, the value of this counter should be as high as possible. If your content can be stored in the HTTP.sys response cache, the value of this counter should be low.

Web Service Cache\URI Cache Hits%

Depends on content. If content cannot be cached in the HTTP.sys response cache, the value of this counter should be as high as possible. If your content can be stored in the HTTP.sys response cache, the value of this counter should be low.

Web Service Cache\URI Cache Misses

Low is better. The value of this counter increases when IIS cannot locate requested content in either the HTTP.sys response cache or the IIS file cache, and must locate the requested content on the hard disk. If the value of this counter is low, responses are being sent from either the IIS file cache or the HTTP.sys response cache.