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11.7 Replication
What: Identify cache entries to be shared. These are likely to be content cached at the servlet level, since that does not contain personalized cache content. Do not replicate any cached JSP fragments that do not have a long life, or are not reusable across users, unless their creation costs are very high.
How: Add an element to their cache entries
<sharing-policy>Value<sharing-policy>See Clustering DynaCache for more details.
Why: In a clustered environment, certain cache entries are highly reusable across users and can be shared among servers in a cluster.
At a minimum use replication to make sure invalidation messages are sent to all members of a cluster and Web pages are showing current information.
Some cache entries are very expensive to recreate, and even with low usage, it can be worth bearing the costs of replication to achieve even a small cache hit rate.
In a dynamic clustered environment (see Appendix | , Caching in WebSphere Extended Deployment), there is the opportunity to partition a very large cache between different members of a cluster, and so increase the proportion of the cache that is held in memory rather than on disk.