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Chapter 10: Processing Integrity and Availability Controls - Coggle…
Chapter 10:
Processing Integrity and Availability Controls
Processing Integrity
Input Controls
form design
all source documents should be sequentially prenumbered
turnaround document
is a record of company data sent to an external party and then returned by the external party for subsequent input to the system
cancellation and storage of source documents
Data Entry Controls
field check
- an edit check that test whether the characters in a field are of the correct field type (e.g., numeric data in numeric fields
sign check
- an edit check that verifies that the data in a field have the appropriate arithmetic sign
limit check
- an edit check that tests a numerical amount against a fixed value
range check
- an edit check that tests whether a data item falls within predetermined upper and lower limits
completeness check (or test)
- an edit check that verifies that all data required have been entered
validity check
- an edit test that compares the ID code or account number in transaction data with similar data in the master file to verify that the accounts exists
reasonableness test
- an edit check of the logical correctness of relationships among data items
check digit
- ID numbers (such as inventory item number) can contain a check digit computed from the outer digits
check digit verification
- recalculating a check digit to verify that a data entry error has not been made
Additional Batch Processing data entry
sequence check
an edit check that determines if a transaction file is in the proper numerical or alphabetical sequence
batch totals
- the sum of a numerical item for a batch of documents, calculated prior to processing the batch, when the data are entered, and subsequently compared with computer-generated totals after each processing step to verify that the data was processed correctly
a
financial total
sums a field that contains monetary values, such as amount of all sales for a batch of sales transaction
a
hash total
sums of nonfinancial field, such as total of the ordered field in a batch sales transactions
a
record count
is the number of records in a batch
Additional Online Data Entry Controls
prompting
- an online data entry completeness check that requests each required item of input data and then waits for an acceptable response before requesting the next required item
closed-loop verification
- an input validation method that uses data entered into the system to retrieve and display other related information so that the data entry person can verify the accuracy of the data input
Processing Controls
data matching
file labels
header record
- type of internal label that appears at the beginning of each file and contains the file name, expiration date, and other file identification information
trailer record
- type of internal label that appears at the end of a file; in transaction files, the trailer record contains the batch totals calculated during input
recalculation of batch totals
transposition error
- an error that results when numbers in two adjacent columns are inadvertently exchanged
cross-footing and zero-balance test
cross-footing balance test
- a processing control that verifies accuracy by comparing two alternative ways of calculating the same total
zero-balance test*
- a processing control that verifies that the balance of a control account equals zero after all entries to it have been made
Write-protection mechanisms
Concurrent update controls
controls that lock out users to protect individual records from errors that could occur if multiple users attempted to update the same record simultaneously
Output Controls
Important output controls:
user review of output
reconciliation procedures
external data reconciliation
data transmission controls
Checksum
- a data transmission control that uses a hash of a file to verify accuracy
Parity bit
- an extra bit added to every character; used to check transmission accuracy
parity checking
- a data transmission control in which the receiving device recalculates the parity bit to verify accuracy of transmitted data
Illustrative Example: Credit Sales Processing
Input Controls
Processing Controls
Output Controls
Processing Integrity Controls in Spreadsheets
Availability
Minimizing risk of system downtime
fault tolerance
- the capability of a system to continue performing when there is a hardware failure
redundant arrays of independent drives (RAID)
- a fault tolerance technique that records data on multiple disk drives instead of just one to reduce the risk of data loss
Common design features:
raised floors provide protection from damage caused by flooding
physical access controls reduce the risk of theft or damage
an
uninterruptible power supply (UPS)
system provides protection in the event of a prolonged power outage, using battery power to enable the system to operate long enough to back up critical data and safely shut down
Recovery and Resumption of Normal Operations
Fundamental questions:
how much data are we willing to recreate from source documents (if they exist) or potentially lose?
how long can be the organizations function without its information system
recovery point objective (RPO)
- the amount of data the organization is willing to reenter or potentially lose
recovery time objective (RTO)
- the maximum tolerable time to restore an organization's information system following a disaster; representing the length of time that the organization is willing to attempt to function without its information system
Data Backup Procedures
Daily partial backups:
1.
incremental backup
- a type of partial backup that involves copying only the data items that have changed since the last partial backup.
differential backup
- type of partial backup that involves copying all changes made since the last full backup
archive
- a copy of a database; master file or software that is retained indefinitely as a historical record, usually to satisfy legal and regulatory requirements
full backup
- exact copy of an entire database
Disaster recovery and Business Continuity Planning
disaster recovery plan (DRP)
- a plan to restore an organization's IT capability in the event that is data center is destroyed
cold site
- a disaster recovery option that relies on access to an alternative facility that is prewired for necessary telephone and internet access, but does not contain any computing equipment
hot site
- a disaster recovery option that relies on access to a completely operational alternative data center that is not only prewired but also contains all necessary hardware and software
real-time mirroring
- maintaining complete copies of a database at two separate data centers and uploading both copies in real-time as each transaction occurs
business continuity plan (BCP)
- a plan that specifies how to resume not only IT operations but all business processes in the event of a major calamity
Effects of virtualization and Cloud computing