- 2.
What is the difference between a record and a page?
A page is the minimum amount of disk storage accessed at a time. It is usually around
1-4 kbytes. A record is the unit of data that a DBMS retrieves. Records can vary in
size. A page may hold several small records, or a large record may be distributed
over several pages.
- 4.
What is clustering? What is the difference between intrafile and interfile
clustering?
Clustering records means to physically store those records that are frequently used
together close together on a disk. Intrafile clustering applies to the clustering of
records that are in a single file. Interfile clustering applies to clustering
records together that are in different files.
An index is a file that contains the values of a field in a file (the index field)
and the address of the field's corresponding record in that file. Thus, an index
file typically contains two fields, one that stores the value of the indexed field
in the original file and one that contains a pointer to the matching record in the
original file.
- 8.
Write the SQL to create an index on the column natcode in the nation table.
CREATE INDEX natcodeindx ON nation (natcode);
- 12.
The national aviation authority in your country has asked you to recommend a data
storage device for its air traffic control system. The specification states that the
file is relatively small (around 500 Mbytes) and system reliability is the foremost
criterion. What would you recommend and why?
Since reliability is critical and storage space requirements quite low, this is a
good case for RAID level 1.
- 14.
A German consumer research company collects scanning data from supermarkets
throughout central Europe. The scanned data include product code identifier, price,
quantity purchased, time, date, supermarket location, and supermarket name, and in some
cases where the supermarket has a frequent buyer plan, it collects a consumer
identification code. It has also created a table containing details of the manufacturer
of each product. The database is very large and contains nearly one Tbyte of data. The
data are used by market researchers in consumer product companies. A researcher will
typically request access to a slice of the database (e.g., sales of all detergents) and
analyze these data for trends and patterns. The consumer research company promises rapid
access to its data. Its goal is to give clients access to requested data within one to
two minutes. Once clients have access to the data, they expect very rapid response to
queries. What data storage and retrieval strategy would you recommend?
This is a situation where the company has a high volume data base but does not
require extremely fast retrieval (1-2 minutes). Mass storage is ideally suited for
such a case, where data are copied from mass storage to magnetic disk as required
for analysis.
- 16.
A video producer has asked for your advice on a data storage device. She has
specified that she must be able to record video at 5 to 7 Mbytes per second. What would
you recommend and why?
RAID is the best solution for this situation. RAID level 3 is probably the best
choice.
- 17a.
Assuming the average size of a digital audio file is 5Mbytes (~ 4 minutes of
music), how much storage space is required?
(1.5*10^6)*(5*10^6) = 7.5*10^12 (i.e., 7.5 Tbytes). There is also the need to
consider storage for backup and recovery and thus you should probably triple this
answer (i.e., 22.5 TBytes)
- 17b.
What storage technology would you recommend?
- 18.
An airline plans to install remote diagnostic systems in its aircraft that will
allow physicians on the ground to remotely monitor an ill passenger. The doctors will
then be able to communicate with flight personnel on appropriate treatment. The system
will send real-time electrocardiogram information, temperature (via an ear probe), blood
pressure information (via a wrist cuff), blood oxygen levels, respiration rates, and
other vital signs to computers at a hospital in Phoenix, Arizona. A built-in modem
connected to a seat-back satellite phone will be used for data transmission. Graphical
help screens will guide flight personnel through every step of the process. Since the
satellite phone operates at only 2.4 kbps, what technology can be used to support this
system?
Data compression, CD-ROM, DVD.
