The ADC is capable of caching data within its internal memory and enhances the delivery of web services. The settings that manage this functionality are provided within this section.
Global Cache Settings
Maximum Cache Size (MB)
This value determines the maximum RAM that the Cache can consume. The ADC Cache is an in-memory cache that is also periodically flushed to the storage medium to maintain cache persistence after restarts, reboots, and shutdown operations. This functionality means that the maximum cache size must fit within the memory footprint of the appliance (rather than disk space) and should be no more than half of the available memory.
Desired Cache Size (MB)
This value denotes the optimum RAM to which the Cache will be trimmed. While the maximum cache size represents the absolute upper boundary of the Cache, the desired cache size is intended as the optimum size that the Cache should attempt to attain whenever an automatic or manual check on the cache size is made. The gap between the maximum and desired cache size exists to accommodate the arrival and overlap of new content between periodic checks on cache size to trim expired content. Once again, it may be more effective to accept the default value (30 MB) and periodically review the size of the Cache under "Monitor -> Statistics" for appropriate sizing.
Default Caching Time (D/HH:MM)
The value entered here represents the life of content without an explicit expiry value. The default caching time is the period for which content without a "no-store" directive or explicit expiry time in the traffic header is stored.
The field entry takes the form "D/HH:MM" – so an entry of "1/01:01" (default is 1/00:00) means to store the ADC will hold the content for one day, "01:00" for one hour, and "00:01" for one minute.
Cacheable HTTP Response Codes
One of the cached data sets is HTTP responses. The HTTP response codes that are cached are:
200 – Standard response for successful HTTP requests
203 – Headers are not definitive but are gathered from a local or a 3rd party copy
301 – The requested resource has been assigned a new permanent URL
304 – Not modified since the last request & locally cached copy should be used instead
410 – Resource is no longer available at the server, and no forwarding address is known
This field should be edited with caution as the most common cacheable response codes are already listed.
Cache Checking Timer (D/HH:MM)
This setting determines the time interval between cache trim operations.
Cache-Fill Count
This setting is a helper facility to help fill the Cache when a certain number of 304's have been detected.
