code: private static OMMapManager createInstance() {
      final OMMapManager localInstance;
      if (OGlobalConfiguration.FILE_MMAP_USE_OLD_MANAGER.getValueAsBoolean()) {
        OLogManager.instance().config(null, "[OMMapManagerLocator.createInstance] Using old mmap manager!");
        localInstance = new OMMapManagerOld();
      } else {
        OLogManager.instance().config(null, "[OMMapManagerLocator.createInstance] Using new mmap manager!");
        localInstance = new OMMapManagerNew();
      }
      return localInstance;
    }
docs: This method called from com.orientechnologies.orient.core.storage.fs.OMMapManagerLocator#getInstance() to create new mmap
  manager and init it.
  
  @return mmap manager instance.