private static DistributedSystem getDistributedSystem() {
    DistributedSystem system = InternalDistributedSystem.getConnectedInstance();
    if (system == null) {
      throw new DistributedSystemDisconnectedException(
          "This connection to a distributed system has been disconnected.");
    }
    return system;
  }
@return true if the method is called on a region has a {@link Pool}.
@since GemFire 6.0
geode-core/src/main/java/org/apache/geode/internal/cache/execute/InternalFunctionExecutionServiceImpl.java