Tuning dynamic cache with the cache monitor

Overview

Use this task to interpret cache monitor statistics to improve the performance of the dynamic cache service.

Verify that dynamic cache is enabled and that the cache monitor application is installed on the appserver.

Use the cache monitor to watch cache hits versus misses. By comparing these two values, we can determine how much dynamic cache is helping the application, and if we can take any additional steps to further improve performance and decrease the cost of processing for the appserver.

 

Procedure

1. Start cache monitor and click on Cache Statistics.

   Cache statistic	Description
   Cache Size	Maximum number of entries that the cache can hold.
   Used Entries	Number of cache entries used.
   Cache Hits	Number of request responses that are served from the cache.
   Cache Misses	Number of request responses that are cacheable but cannot be served from the cache.
   LRU Evictions	Number of cache entries removed to make room for new cache entries.
   Explicit Removals	Number of cache entries removed or invalidated from the cache based on cache policies or were deleted from the cache through the cache monitor.

2. We can also view the following cache configuration values:

   Cache configuration value	Description
   Default priority	Default priority for all cache entries. Lower priority entries are moved from the cache before higher priority entries when the cache is full. We can specify the priority for individual cache entries in the cache policy.
   Servlet Caching Enabled	If servlet caching is enabled, results from servlets and JSPs files are cached.
   Disk Offload Enabled	Specifies if entries that are being removed from the cache are saved to disk.

3. Wait for the appserver to add data to the cache.

   You want the number of used cache entries in the cache monitor to be as high as it can go. When the number of used entries is at its highest, the cache can serve responses to as many requests as possible.

4. When the cache has a high number of used entries, reset the statistics. Watch the number of cache hits versus cache misses. If the number of hits is far greater than the number of misses, the cache configuration is optimal. You do not need to take any further actions. If we find a higher number of misses with a lower number of hits, the appserver is working hard to generate responses instead of serving the request using a cached value. The appserver might be making database queries, or running logic to respond to the requests.

5. If we have a large number of cache misses, increase the number of cache hits by improving the probability that a request can be served from the cache.

   To improve the number of cache hits, we can increase the cache size or configure additional cache policies.

 

Next steps

See Task overview: Using the dynamic cache service to improve performance

 

Related concepts

Cache monitor

 

Related tasks

Troubleshooting the dynamic cache service
Displaying cache information