|
(a) Define the following
terms and, in each case, provide a suitable example to
illustrate your answer. [6]
(i) Master file.
(ii) Reference file.
(iii) Security file.
(a) In each case, one mark should be awarded
for a satisfactory description
and a further mark should be awarded for a suitable example.
(i) A master file is a relatively permanent file that relates to a
standard
entity in the system (1 mark). An example of a master file is a file
containing patient records (1 mark).
(ii) A reference file is a file, the contents of which are relatively
stable,
but still subject to change (1 mark). An example of a reference file
is the personal income tax rate (1 mark).
(iii) A security file is a file that is created for backup and recovery
purposes (1 mark). An example of a security file is an audit trail
file (1 mark).
Other correct answers should also receive credit. [6 marks]
(b) Define the term audit trail. [2]
(b) An audit trail is a series of records
that can be used for tracking data (1
mark). If verification is required at any time, then results of output
can be
traced back to the point of input (1 mark).
Other correct answers should also receive credit. [2 marks]
(c) (i) Describe two types of file control.
[4]
(ii) In the context of file controls, what do the terms rollback and
bringing
forward the files mean? [3]
(c) (i) For each of the following, one mark
should be awarded for naming
the technique, and a further mark should be awarded for a satisfactory
elaboration:
- Include a grand total as the last record of the master file (1 mark).
As transactions are processed, the totals of transactions are accumulated;
the value of the beginning grand total plus the accumulated transaction
total is compared to the value of the new grand total; processing
may continue only if the values are equal (1 mark).
- Identify all fields that are necessary to reconstruct the current
versions of the critical application files (1 mark). The critical
files are those which are necessary to ensure continued operation;
backup files are used to reconstruct critical application files if
the originals are damaged or destroyed (1 mark).
[4 marks]
(ii) Before images (copies of the master file records prior to a transaction)
and after images (copies of master file records following a transaction)
provide sufficient information to reconstruct records if they are
damaged (1 mark). If a transaction has changed certain records improperly,
then it may be rolled back, i.e., run in reverse to a point at which
the records are in a
correct state (1 mark). Bringing forward the files, on the other hand,
involves making before images current by reprocessing them with copies
of transactions (1 mark).
[3 marks]
|