DCIT55 (LEC) | Finals

Question 1

mechanisms for restoring a database quickly and accurately after loss or damage

Answer 1

database recovery

Question 2

provide backup copies of portions of the entire database and you can use operating system commands, or SELECT . . . INTO SQL commands to perform backups

Answer 2

backup facilities

Question 3

full backup of a database

Answer 3

cold backup

Question 4

only a selected portion of the database is shut down from use

Answer 4

hot backup

Question 5

maintain an audit trail of transactions and database changes

Answer 5

journalizing facilities

Question 6

by which DBMS periodically suspends all processing and synchronizes its files and journals to establish a recovery point

Answer 6

checkpoint facility

Question 7

all transactions in progress are completed, and the journal files are brought up to date

Answer 7

checkpoint facility

Question 8

allows the DBMS to restore the database to a correct condition and restart processing transactions when a failure occurs and then resumes processing user questions

Answer 8

recovery manager

Question 9

at least two database copies must be kept and updated simultaneously. When a media failure occurs, the processing is switched to a duplicate database copy

Answer 9

disk mirroring

Question 10

a technique that involves reprocessing the day’s transactions (up to the point of failure) against the backup copy of the database

Answer 10

restore/rerun

Question 11

a sequence of steps that constitute some well-defined business activity

Answer 11

business transaction

Question 12

Normally, it requires several actions against the database

Answer 12

business transaction

Question 13

When processing transactions, the DBMS must ensure that the transactions follow four well-accepted properties called the

Answer 13

ACID properties

Question 14

The transaction cannot be subdivided, and hence, it must be processed in its entirety or not at al

Answer 14

atomic

Question 15

Any database constraints that must be true before the transaction must also be true after the transaction

Answer 15

consistent

Question 16

Changes to the database are not revealed to users until the transaction is committed

Answer 16

isolated

Question 17

Changes are permanent

Answer 17

durable

Question 18

The back out, or undo, of unwanted changes to the database

Answer 18

backward recovery/rollback

Question 19

Used to reverse the changes made by transactions that have aborted, or terminated abnormally

Answer 19

backward recovery/rollback

Question 20

A technique that starts with an earlier copy of the database

Answer 20

forward recovery/roll forward

Question 21

it (the results of good transactions) quickly moves the database to a later state

Answer 21

after-images

Question 22

➢ A transaction in progress that terminates abnormally.
➢ Human error, input of invalid data, hardware failure, and deadlock
➢ Recovery technique: rollback

Answer 22

aborted transactions

Question 23

➢ When the error data have been processed, the database may be recovered in one of the following ways:
a. If the error is discovered soon enough, backward recovery may be used.
b. If only a few errors have occurred, a series of compensating transactions may be introduced through human intervention to correct the errors.
c. If the first two measures are not feasible, it may be necessary to restart from the most recent checkpoint before the error occurred, and subsequent transactions processed without the error.
➢ Recovery technique: rollback

Answer 23

incorrect data

Question 24

➢ Some components fail, but the database is not damaged.
➢ Power loss, operator loss, loss of communications transmission and system software failure.

Answer 24

system failure

Question 25

➢ The database itself is lost, destroyed, or cannot be read. ➢ Disk failure

Answer 25

database destruction

Question 26

➢ A natural or manmade disaster

Answer 26

disaster recovery

Question 27

Allow other transactions to read (but not update) a record or other resources

Answer 27

s-lock/shared lock

Question 28

Prevent another transaction from reading (and therefore updating) a record until it is unlocked

Answer 28

x-lock/exclusive lock

Question 29

An impasse that results when two or more transactions have locked a common resource, and each wait for the other to unlock that resource

Answer 29

deadlock

Question 30

any data that are retrieved by a user for updating must be locked, or denied to other users until the update is completed or aborted

Answer 30

locking