chapter20 实践习题2
需积分: 0 22 浏览量
2022-08-03
15:04:22
上传
评论
收藏 1.34MB PDF 举报
C H A P T E R
20
Database-System Arhitetures
Solutions for the Pratie Exerises of Chapter 20
Pratie Exerises
20.1
Answer:
No. A single proessor with only one ore an run multiple proesses to man-
age mutiple users. Most moder n systems are parallel, however.
20.2
Answer:
The memor y fene ensures that the proess that gets the mutex will see all
updates that happened before the instrution, as long as proesses exeute
a fene before releasing the mutex. Thus, even if t he data was updated on a
dierent ore, t he proess that aquires the mutex is guaranteed to see the
latest value of the data.
20.3
Answer:
The drawbaks would be t hat two interproess messages would be required
to aquire loks, one for the request and one to onr m grant. Inter proess
ommuniation is muh more expensive than memor y aess, so the ost of
loking would inrease. The proess stor ing the shared str utures ould also
beome a bottlenek.
The benet of this alternative is that the lok table is proteted better from
erroneous updates sine only one proess an aess it.
131
评论0