问题 多项选择题

您的用户报告“ORA-1555:snapshot too old(快照过旧)”错误消息。这个错误可能是由下列哪些原因造成的(选择一个最佳答案)?

A.没有足够频繁地生成快照

B.撤销数据过旧

C.没有足够的撤销数据

D.撤销表空间保存数据的时间过长

答案

参考答案:C

解析:“ORA-1555:snapshot too old(快照过旧)”错误明确指出,撤销数据的保存时间不够长,不足以满足查询工作负载的要求:没有足够的可用撤销数据。A是错误的,因为它根本不指撤销,指的是快照(存在于早先的数据库版本中,现称为物化视图)。B和D都是错误的,因为它们描述了相反的情形:撤销数据的保留时间过长。这不是问题,但可能浪费空间。

单项选择题

After winning a big game, athletes are often asked how they feel. Usually athletes say how (1) it is to win this big game. On the contrary, the fact is that losing a big game, or in my case, all the games, can be even harder.

From the spectators’ point of view, last year’s basketball (2) for my high school team was nothing (3) of an embarrassment. And (4) 0 and 20 is certainly nothing to be proud of, that season had a bigger impact on me than any other. As a team captain, I knew it probably wouldn’t be the (5) year, but did I ever think we would lose every game Of course not. Since six of our top players had graduated, it was clear that we were a (n) (6) team who would struggle. The struggle began earlier than expected, (7) , as our team center was suspended (禁赛) for the season, and two key members decided to (8) for some reason. At this point, dropping out probably passed through every player’s mind, but in the end, we all stuck if out, (9) to work still harder.

Then there came a time when even our (10) and given up on us. Personally, I felt like it was (11) worthwhile giving my all. I thought, if even the coach doesn’t believe in us, why should I But just as my hope began to (12) , a teammate called a meeting. He said," Nobody thinks we are going to win, but, as teammates and friends, we (13) it to each other to go all out every game. "

It was that moment that (14) me how to be a leader. It hit me that I certainly didn’t (15) the role. As a leader you can never quit (16) the team who looks up to you. It is one (17) to be named captain, feel great and go through the motions, but it is quite another to be a real captain and make sure everyone realizes their full (18) all the time.

I am sure it is great to go through without losing and bringing home awards. But in all honesty, I (19) the fact that my team lost every game last year. It may not help me to become a better basketball player, but it already has made me a better leader, and (20)

11().

A.only too

B.more than

C.not a little

D.no longer

单项选择题