docs: def guest_register(self, userid, meta, net_set):
          """DB operation for migrate vm from another z/VM host in same SSI
          :param userid: (str) the userid of the vm to be relocated or tested
          :param meta: (str) the metadata of the vm to be relocated or tested
          :param net_set: (str) the net_set of the vm, default is 1.
          """
          userid = userid.upper()
          if not zvmutils.check_userid_exist(userid):
              LOG.error("User directory '%s' does not exist." % userid)
              raise exception.SDKObjectNotExistError(
                      obj_desc=("Guest '%s'" % userid), modID='guest')
          else:
              action = "list all guests in database which has been migrated."
              with zvmutils.log_and_reraise_sdkbase_error(action):
                  guests = self._GuestDbOperator.get_migrated_guest_list()
              if userid in str(guests):
                  """change comments for vm"""
                  comments = self._GuestDbOperator.get_comments_by_userid(
                                                                      userid)
                  comments['migrated'] = 0
                  action = "update guest '%s' in database" % userid
                  with zvmutils.log_and_reraise_sdkbase_error(action):
                      self._GuestDbOperator.update_guest_by_userid(userid,
                                                      comments=comments)
              else:
                  """add one record for new vm"""
                  action = "add guest '%s' to database" % userid
                  with zvmutils.log_and_reraise_sdkbase_error(action):
                      self._GuestDbOperator.add_guest_migrated(userid, meta,
                                                               net_set)
                  action = "add switches of guest '%s' to database" % userid
                  info = self._vmops.get_definition_info(userid)
                  user_direct = info['user_direct']
                  for nic_info in user_direct:
                      if nic_info.startswith('NICDEF'):
                          nic_list = nic_info.split()
                          interface = nic_list[1]
                          switch = nic_list[6]
                          with zvmutils.log_and_reraise_sdkbase_error(action):
                              self._NetworkDbOperator.switch_add_record_migrated(
                                  userid, interface, switch)
              LOG.info("Guest %s registered." % userid)