定期维护

• In the 70 ' s and 80 ' s , because these data were stored in the expensive middle or mini computers and the system manager had to back up the data periodically , the enterprise cost a lot . on the other hand , once these machines were out of work , the services provided by these machines had to be interrupted and the enterprise suffered big loss
  七、八十年代，这些数据都被存放在昂贵的中小型机中，由管理员定期维护其中的数据，但这需要较大的投资，且一旦机器出现故障，将会中断系统服务，给企业造成损失。