3.3 CRM (Doshi) Flashcards
What is a check digit?
A mathematically calculated value that is added to data to ensure that the original data haS not been altered
Why check digit?
This helps in avoiding transposition and transcription errors.
Parity Bit
A method of error detection, it requires adding an extra bit (called parity bit) on the data.
Why would a parity bit be used?
It’s received by computer to ensure data completeness and data integrity during transmission.
Parity check
Is a hardware control that detects data errors when data is read from:
(1) one computer to another,
(2) from memory
(3) or during transmission.
Checksums
- Programs that compute checksums can be run against old and new databases to ensure the accuracy of migrated data.
- Checksum ensure is data copied is the same as original
Cyclic Redundancy Checksums (CRC)/Redundancy Checksums
A more advanced version of checksums by increasing the complexity of the arithmetic
Forward Error Control
Works on same principle as CRC. However FEC also corrects the error. FEC provides the receiver with the ability to correct errors.
Atomicity:
Atomicity is a feature of databases systems where a transaction must be all-or-nothing.
(That is, the transaction must either fully happen, or not happens at all.)
When should a check digit be performed?
(1) When the objective is to identify transcription and transposition error.
(2) When the objective is to ensure accuracy,
What relevant controls MUST be performed when the objective is to identify transmission error?
(1) First preference is CRC
(2) If no CRC, them checksum,
(3) If no CRC and no checksum,
(4) Then, parity bit
What relevant controls are required to perform when objective is to ensure completeness?
First preference is CRC
If no CRC, them checksum,
If no CRC and no checksum,
Then, parity bit
What relevant control should be performed when the objective is to ensure integrity?
First preference is CRC
If no CRC, them checksum,
If no CRC and no checksum,
Then, parity bit
What relevant control should be performed when the objective is to correct (detect &correct) a transmission error?
Forward Error Control (FEC)
When should atomicity be performed?
To ensure that a transaction must either fully happen, or not happens at all.
Check digit example:
Example:
Check digit is used by bank to ensure the correctness of bank account numbers assigned to customers, thereby helping to avoid transposition and transcription errors.
For instance, a bank account number is “630000241457”. The last digit is the check digit “7”, and if the other numbers are correct then the check digit calculation must produce 7.
Add the odd number digits: 6+0+0+2+1+5 = 14.
Multiply the result by 3: 14 × 3 = 42.
Add the even number digits: 3+0+0+4+4 = 11.
Add the two results together: 42 + 11 = 53.
To calculate the check digit, take the remainder of (53 / 10), and if not 0, subtract from 10. Therefore, the check digit value is 7.
When objective is to identify transcription and transposition error, answer should be
check digit.
When objective is to ensure accuracy, answer should be
check digit.
When objective is to identify transmission error, answer should be
parity bits or checksum (higher version of parity bit) or CRC (higher version of checksum).
When objective is to ensure completeness, answer should be
parity bits or checksum (higher version of parity bit) or CRC (higher version of checksum).
When objective is to ensure integrity, answer should be
parity bits or checksum (higher version of parity bit) or CRC (higher version of checksum).
For point no. (3), (4) and (5), first preferences to be given as follow:
(i) First preference to CRC
(ii) If CRC is not there as option then preference to be given to Checksum
(iii) If CRC and Checksum both are not there in option then preference to be given to Parity Bits.
When objective is to correct (detect & correct) transmission error,
answer should be Forward Error Control (FEC).
When objective is to ensure that a transaction must either fully happen, or not happens at all, answer should be
atomicity.
