code: @Deprecated
      public CommandResult fsync(final boolean async) {
          DBObject command = new BasicDBObject("fsync", 1);
          if (async) {
              command.put("async", 1);
          }
          return getDB(ADMIN_DATABASE_NAME).command(command);
      }
docs: Forces the master server to fsync the RAM data to disk This is done automatically by the server at intervals, but can be forced for
  better reliability.
  
  @param async if true, the fsync will be done asynchronously on the server.
  @return result of the command execution
  @throws MongoException if there's a failure
  @mongodb.driver.manual reference/command/fsync/ fsync command