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HTTP allows a browser, or another user agent, to communicate with different resources on the Internet: to do this the browser needs both the identity and the location of the resources. Information on the identity and the location of the resources is described by a Uniform Resource Identifier (URI). URIs enable internet protocols to unambiguously identify and locate websites or other web-connected resources. To significantly improve the performance of web sites and applications, frequently accessed URIs are cached and reused to access previously fetched resources on the server. The URI cache reduces latency and network traffic and thus lessen the time needed to display resource representations. Moreover, the URI cache makes the Web sites or other web-connected resources more responsive. Direct requests to fetch the resources on the target server are expensive operations, which may result in an increase in processing overheads and latencies, and eventually, degrade the overall performance of the server as well as the user experience with the target server. The primary focus of administrators therefore is to improve the URI cache usage, so that direct resource accesses are kept at a minimum.

By closely monitoring the requests to access the resources on the target server through HTTP and reporting the fraction of requests that have been serviced by the URI cache, this test reveals whether/not the URI cache has been effectively utilized. If the URI cache utilization is found to be low, then, it may indicate an increase in processing overhead on the target server. This way, this test proactively alerts administrators to find out the root cause for low cache utilization and initiate remedial measures to fine-tune URI cache before the processing overhead causes serious impact on use experience.

Outputs of the test : One set of results for the target server being monitored.

Measurement	Description	Measurement Unit	Interpretation
Current_uris_cache	Indicates the number of URIs that are currently cached on the target server.	Number	The performance of applications can be significantly improved by reusing previously fetched resources. Cached URLs reduce latency and network traffic and thus lessen the time needed to display resource representations. HTTP caching makes Web sites more responsive.
Total_flush_uris	Indicates the number of URIs that were removed from the kernal during the last measurement period.	Number
Total_uris_cache	Indicates the number of URIs that were added to the kernal during the last measurement period.	Number
Uri_cache_flushes	Indicates the number of URI cache flushes that have occurred since the server started.	Number
Uri_cache_hits	Indicates the number of URI requests serviced by the cache during the last measurement period.	Number	A high value is preferred for this measure.
Uri_cache_misses	Indicates the number of URI requests serviced by origin server during the last measurement period.	Number	Ideally, the value of this measure should be 0 or much lower than the value of the URI cache hits measure. A very high value is a cause for concern as it indicates that the cache is poorly utilized.
Hits_ratio	Indicates the percentage of URI requests that were serviced by this URI cache during the last measurement period.	Percent	Ideally, the value of this measure should be 80% and above. A value lesser than 80% indicates that the cache is unable to service many URI requests, maybe because the URIs requested are not in cache. This could be due to poor cache size.