问题 单项选择题

设有两个事务T1和T2,其并发操作序列如下表所示。则下面说法中正确的是________。

A.该操作序列不存在问题

B.该操作序列丢失更新

C.该操作序列不能重复读

D.该操作序列读出“脏”数据

答案

参考答案:B

解析:[评析] 由表可知,T1读取了数据项A,然后T2也读取了数据项A,它们读到的值都为100。随后事务T1对数据项A进行更新,在刚才读的基础上A的值加10,然后事务T2对数据项A进行更新,在刚才写的基础上A的值减 10。当事务T2对数据项A进行更新时,事务T1所做的更新丢失了,被事务T2所做的更新覆盖了。

选择题
阅读理解

阅读理解

     [1] I was walking in the park with a friend recently,and his cell phone rang,interrupting our

conversation.There we were,walking and talking on a beautiful sunny day.But I became invisible,absent

from the conversation.

     [2] The telephone used to connect you to the absent.Now it makes people sitting next to you  feel

absent.Recently I was in a car with three friends.The driver told us to be quiet because he could not hear

the person on the other end of his cell phone.There we were,four friends going down the highway,unable

to talk to one another because of a tool designed to make  communication easier.

     [3] Why is it that the more connected we get,____________?Every advance in  communications

technology is a hurt to the closeness of human interaction (互动). With email and instant messaging over

the Internet,we can now communicate without seeing or talking to one another.With voice mail,you can

conduct entire conversations without ever reaching anyone.

     [4] More_and_more,I_find_myself hiding_behind_email to_do_a_job_ meant_for conversation.Or

being relieved that voice mail picked up because I didn't really have time to talk.The industry devoted to

helping me keep in touch is making me lonelier.

     [5] So I've put myself on technology restriction:no instant messaging with people who live near me,no

cellphoning in the presence of friends,no letting the voice mail pick up when I'm home.

1. What does the author say about communications technology according to the first two paragraphs?

(within 15 words)

________________________________________________________________________

2. Which sentence in the text is the closest in meaning to the following one?

However,I felt left out as if we were not conducting the conversation.

________________________________________________________________________

3. Fill in the blank in Paragraph 3 with proper words.(within 10 words)

________________________________________________________________________

4. Does the author restrict his own activity to improve the situation?Give an example.(within 15 words)

________________________________________________________________________

5. Translate the underlined sentence in Paragraph 4 into Chinese.

________________________________________________________________________