问题 填空题

在关系数据库中,可以对属性值、属性值集合、元组、关系、整个索引、整个数据库等逻辑单元进行加锁,也可以对数据页、索引页和块等物理单元进行加锁,这些施加了锁的数据项的大小称为______。

答案

参考答案:[14]锁粒度

解析: 这是对锁粒度概念的考查,锁粒度与事务并发执行的程度和DBMS并发控制的开销有密切的联系,锁粒度越大,系统中可以被加锁的数据项就越少,事务并发执行度就越低,同时系统开销也就越小;反之,锁粒度越小,系统开销越大。

填空题
单项选择题

At some time in your life you may have a p desire to do something strange or terrible. However, chances are that you don’t act on your impulse, but let it pass instead. You know that to commit the action is wrong in some way and that other people will not accept your behavior.
Perhaps the most interesting thing about the phenomenon of the behavior is how it can change over the years within the same society, how certain behavior and attitudes once considered taboo can become perfectly acceptable and natural at another point in time. Topics such as death, for example, were once considered so upsetting and unpleasant that it was a taboo to even tall about them. Now with the publication of important books such as "On Death and Dying" and "Learning to Say Goodbye", people have become more aware of the importance of expressing feelings about death and, as a result, are more willing to talk about this taboo subject.
One of the newest taboos in American society is the topic of fat. Unlike many other taboos, fat is a topic that Americans tall about constantly. It’s not taboo to tall about fat; it’s taboo to be fat. The "thin" look is thin, not fat.
In the work world, most companies prefer youthful-looking, trim executives to sell their image as well as their products to the public. The thin look is associated with youth, vigor and success. The fat person, on the other hand, is thought of as lazy and lacking in energy, self- respect. After all, people think, how can people who care about themselves, and therefore the way they look, permit themselves to become fat In an image-conscious society like the U.S., thin is "in", fat is "out".

Which of the following statements is TRUE according to the passage

A. Death is a taboo topic today.
B. It is taboo to talk about fat.
C. The topic of fat is different from many other taboo subjects.
D. Fat is a topic that Americans talk about very little.