8.5.  Configure and monitor the WebSphere Application Server caching mechanisms.


Dynamic caching

WebSphere Application Server, by using the dynamic cache, provides the caching of the output of servlets, JSP, portlets, or web services. Dynamic caching is an in-memory cache with the ability to offload the content on disks. If you decide to offload the content, use fast I/O storage.

Dynamic caching is enabled at the container services level of the application server. Objects that can be cached are defined inside the cachespec.xml file. This file is stored inside the web module WEB-INF or enterprise bean META-INF directory. The caching options in the cachespec.xml file must include sufficient details to allow the dynamic cache service to build a unique cache-key. This cache-key is used to uniquely identify each object, which can be achieved by specifying request parameters, cookies, and so on. With the cachespec.xml file, you can define cache invalidation rules and policies.

You can also share the cache data with the other servers of the cluster. By using the functions that are provided by the DRS (Data replication service), you can replicate or copy the data to the other members of the cluster. This process saves execution time and resources. The cache consistency is maintained by the DRS. If a cache entry is invalidated by one server, the invalidation is propagated to all the members.

The cache monitor application is available to manage the data, and monitor and verify the configuration of the dynamic cache. It must be installed as a normal application.

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