This manual is for an old version of Hazelcast IMDG, use the latest stable version.
Chapter 3. Elastic Memory (Enterprise Edition Only)

Chapter 3. Elastic Memory (Enterprise Edition Only)

By default, Hazelcast stores your distributed data (map entries, queue items) into Java heap which is subject to garbage collection. As your heap gets bigger, garbage collection might cause your application to pause tens of seconds, badly effecting your application performance and response times. Elastic Memory is Hazelcast with off-heap (direct) memory storage to avoid GC pauses. Even if you have terabytes of cache in-memory with lots of updates, GC will have almost no effect; resulting in more predictable latency and throughput.

Here are the steps to enable Elastic Memory:

If NearCache is defined for a map, all near cached items are also going to be stored on the same off-heap. So off-heap storage is used for both near cache and distributed object storage.

Also see how to configure license key.