问题 单项选择题

为了保证数据库中数据的安全可靠和正确有效,数据库管理系统(DBMS)提供数据库恢复、并发控制、数据完整性保护与数据安全性保护等功能。数据库在运行过程中由于软硬件故障可能造成数据被破坏,数据库恢复就是在尽可能短的时间内把数据库恢复到故障发生前的状态。具体的实现方法有多种,如定期为数据库制作 (6) ;在进行事务处理时,对数据更新(插入、删除、修改)的全部有关内容写入 (7) ;在系统正常运行时,按一定的时间间隔设立 (8) ,把内存缓冲区内容还未写入到磁盘中去的有关状态记录到 (8) 中;当发生故障时,根据现场数据内容、 (9) 的故障前映像和 (10) 来恢复系统的状态。

A.库文件

B.日志文件

C.检查点文件

D.后备文件

E.主文件 源程序 流文件 作业

答案

参考答案:D

单项选择题
单项选择题

There is virtually no limit to how one can serve community interests, from spending a few hours a week with some charitable organization to practically full-time work for a social agency. Just as there are opportunities for voluntary service (1) (VSO) for young people before they take up full-time employment, (2) there are opportunities for overseas service for (3) technicians in developing countries. Some people, (4) those who retire early, (5) their technical and business skills in countries (6) there is a special need.

So in considering voluntary or (7) community service, there are more opportunities than there (8) were when one first began work. Most voluntary organizations have only a small full-time

(9) and depend very much on volunteers and part-timers. This means that working relationships are different from those in commercial organizations, and values may be different. (10) some ways they may seem more casual and less efficient, but one should not (11) them by commercial criteria. The people who work with them do so for different reasons and with different (12) , both personal and (13) . One should not join them (14) to arm them with professional experience; they must be joined with commitment to the (15) , not business efficiency. Because salaries are (16) or non-existent many voluntary bodies offer modest expense. But many retired people take part in community service for (17) , simply because they enjoy the work.

Many community activities possible (18) retirement were also possible during one’s working life but they are to be undertaken (19) seriously for that. Retired people who are just looking for something different or unusual to do should not consider (20) community service.

19()

A. much

B. very much

C. no more

D. no less