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A RAM cache is a cache of HTTP objects stored in the BIG-IP systems random-access memory (RAM) that subsequent connections can reuse to reduce the amount of load on the backend servers. The RAM cache feature provides the ability to reduce the traffic load to backend servers. This ability is useful if an object on a site is under high demand, if the site has a large quantity of static content, or if the objects on the site are compressed. For compressible data, the RAM cache can store data for clients that can accept compressed data. When used in conjunction with the compression feature on the BIG-IP system, the RAM cache takes stress off the BIG-IP system and the content servers. If the RAM cache is not adequately sized or is not able to cater to the requests, then the backend servers may be overloaded with requests defying the very purpose of the cache. Therefore, it is necessary to constantly keep track of the cache. The LtmRamCacheTest test helps administrators in this regard!

Using this test, administrators can figure out the average percentage of data that was serviced by the RAM cache, the percentage of bytes that were serviced from the RAM cache etc. In addition, this test also helps administrators identify the percentage of data that was removed from the RAM cache.

Outputs of the test : One set of results for the target traffic manager that is being monitored.

Measurement	Description	Measurement Unit	Interpretation
Hit_rate	Indicates the percentage of data that was serviced from the RAM cache.	Percent	Ideally, the value of this measure should be high. A low value indicates that many read requests are serviced by direct disk accesses, which is a more expensive operation in terms of processing overheads.
Avg_hit_rate	Indicates the average percentage of data that was serviced from the RAM cache.	Percent	A high value is desired for this measure.
Byte_rate	Indicates the percentage of bytes that were serviced from the RAM cache.	Percent
Avg_byte_rate	Indicates the average percentage of bytes that were cached in the RAM cache.	Percent
Eviction_rate	Indicates the percentage of data that was removed from the RAM cache.	Percent	A low value is desired for this measure. A higher value of this measure may be an indication of outdated entries in the cache which should be evicted from the cache to accommodate new cache entries.
Avg_eviction_rate	Indicates the average percentage of data that was removed from the RAM cache.	Percent