Why and when to perform this task
In a clustered environment, the content you place in cache might be shared with other servers in the cluster. The content might also be off-loaded to disk. If you intend to have the cached objects shared or off-loaded to disk, you must make these particular objects serializable. If the objects you place in cache are non-serializable, you must specify that the sharing policy for these objects is "not shared". The DistributedMap interface Javadoc contains information about how to specify the sharing policy for a cached object. Specifying a sharing policy other than "not shared" for non-serializable objects can result in poor system performance.