A cache is an in-memory storage area. In OEP, a cache is often used to store events. While it is not strictly necessary to use a cache in your application, it can significantly improve performance over retrieving data from the database.
In Chapter 4, Assembling and Configuring OEP Applications, we briefly looked at how to set up a caching system. Now we'll cover that in a little more detail.
A caching system is a configured instance of a caching implementation. A caching system includes the configuration information needed to connect to one or more named caches defined in the caching system. Setting up Coherence requires specific configuration files which must also be made available to the OEP JVM, just as they would need to be part of the configuration of any Coherence JVM that is part of the cluster. This is a rich topic which you should learn more about if you plan to implement caching within OEP. A good place to start to experiment with the different configurations...