Introduction to Database Systems
The following homework was distributed last thursday, BUT we are
running behind (more behind) than i thought. so, it won't be due
til the following week (maybe tuesday, if we catch up).
In the meantime, so you stay 'on top' of things - work on study
questions for the chapters we've done, and work on getting your
lab database 'in shape'.
Homework 3
due: Thursday Jan. 29
-
(10 points) Disks have hidden tracks, usually clustered near the spindle.
If there is a bad sector in a regular track, that sector is remapped to a
location in one of the hidden tracks. The bad sector map is usually held in the
disk controller during operation and the controller uses it to redirect read and
write requests for bad sectors.
Disk mirroring is a technique to cope with media failure on secondary storage.
A pair of disks are run in tandem. Their contents are kept identical by doing
all disk writes to both disks (at the same location).
Explain how hidden remapping can create performance problems with disk
mirroring. Suggest a modification (either to bad sector remapping or disk
mirroring) that could ameliorate this performance problem.
UNIX Potluck
Assignment #3
Due January 29th
points are indicated in parentheses
Basic
- (3) Write a web page and a corresponding perl script tha sends users to
a web site that is chosen randomly from the list of sites that your
program keeps.
- (2) Implement a visible counter on a web page using CGI and Perl. The
message on the web page could say something like "You are visitor
number ___.." Your Perl program will need to store information in a
file.
- (3) Design a form (or forms) in HTML that can be used to input
information about an event and/or retrieve information about events.
(Note this is HTML only -- no need to write scripts for processing the
information.)
Super User
- Write a web page and a corresponding perl script tha sends users to
a web site that is chosen randomly from the list of sites that your
program keeps based on URLs that users have supplied via a form on your
web site.
- (3) Implement an HTML file "detagger" using Perl. The role of this
software tool is to derive a plain text file from an HTML tagged file.
Since we may wanti to reintroduce the tags into the file ("retag") at a later date we will
need to store all the necessary information. This includes the plain
("detagged") file and the necessary tags and locations of tags. (Hint:
first write a script that actually finds every HTML tag -- there may of
course be more than one per line.)
- (2) Implement a invisible record of hits to your web page using CGI and
Perl. The information should include information about what type of
browser was used and where they came from. This information should be
stored in such a way that other Perl (or awk or other) tools could
access it easily for re-use in web pages or other reports.
Wizard
- (3) Develop the "retagger" software tool. This tool will take a plain
text file and the tags & tag location file(s) and will recreate an HTML
file that is identifical to the original tagged file.
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