Transaction Processing Systems

1. Mr Zarkovic
Transaction Processing Systems

2. Option Topics
Students must study a minimum of two option
topics
Students are able to study more than two option
topics
However many teachers find this difficult to
achieve given the time constraints on the course
As well, many students would protest at having
to do more than the minimum without a good
reason

3. Option Topics
Which option topics you choose will
depend to a large extent on the resources
available at the school
It would also depend on the experience
and expertise of the teacher taking the
course
And also on the abilities and interests of
the students

4. Option Topics
Based on personal experience and anecdotal
evidence obtained by talking with teachers at
other schools, it appears that the option topics
studied by most schools, in order of preference
are:
 Multimedia systems (Most schools)
 Decision support systems
 Transaction processing systems
 Automated Manufacturing Processing Systems (Least
number of schools)

5. Option Topics
At AGHS, we study:
 Multimedia Systems
 Decision Support Systems
as we feel this provides our students with:
 A broad base of experience
 Ample practical experiences to keep students
motivated and interested

6. Transaction Processing Systems
(TPS)
In this lecture I will be covering those
aspects of the syllabus that may require
clarification and will suggest a few support
activities
Although this topic is critical in the modern
workplace, there is not a lot of scope for
practical exercises, beyond the
consolidation of database skills

7. What is a TPS?
A TPS records and manages all the data
collected or generated by an organisation
in its day to day operations
Examples
 Orders, invoices, wages, employee records
A TPS does not generate information
The data from a TPS is mostly used as
input to other information systems

8. Why teach this topic?
The amount of content in this topic is not
onerous. In fact most of it seems to be an
extension of the core topic Database
Information Systems
There is a lot of theory in this topic - this
may be an advantage if your school lacks
resources for other option topics or you
lack confidence with the teaching of other
option topics

9. Disadvantages with this topic
There is a lot of theory. Without many
practical experiences, some students will
get bored
Some students will see this topic as a
rehash of the Database topic

10. Batch vs Real Time Processing
Data processing can be of two types:
 Batch
 Real time
Students need a clear understanding of
the difference between these two types of
processing

11. Batch Processing
Transaction data is collected and stored
At a later time the transaction data is processed
In the early days of computing this was how data was processed
Programs were written on ‘punched cards’
The first part of the stack of cards had the actual program while the
second part of the stack of cards contained the data
e.g. back in the 70’s (the not-so-good old days) programs were
written in Fortran IV using this approach, there was no ‘being on-
line’. Student assignments were run overnight and the results
available the next day. If a comma was in the wrong place that card
would have to be re-punched and the program run again the next
night - no such thing as doing an assignment at the last minute and
one certainly learnt to plan carefully and pay attention to detail!

12. Batch Processing
Batch processing is still a common way of
processing data e.g. the national census
These days, data is collected and stored in a
data file, often by data entry operators
These data files are then processed when the
demand on the organisation's computers is
lowest, usually at night
One of the drawbacks with this type of
processing is if a problem occurs (such as
incompatible data) all execution of the program
halts

13. Real Time Processing
All transactions are processed as they
occur, interactively
This enables a result to be obtained
immediately
For example, when using a joystick to
control a flight simulator, a movement of
the stick, results in an immediate change
to the graphic on the screen

14. Examples of transaction processing
systems
Some examples suggested by the
syllabus include reservation systems,
point of sale terminals and library loans
Ware, Cheleski and Chivers’ book does
an excellent job examining the various
components of all of these systems

15. Storage and Retrieval

16. Storage & retrieval of digital data in
databases and files
Three types of storage students should be
aware of:
 Sequential data storage
 Indexed sequential data storage
 Hashed file storage

17. Sequential data storage
This involves writing the data to a data file
on a medium one character after another
For databases, records are stored one
after the other
When backing up data to a tape drive, the
data is often saved in sequential form

18. Searching for data
Two methods are commonly used to
search for data in a sequential file
First Method :Linear Search
 To find a particular record the search starts by
scanning the first record, then the next, and
so on until the required record is located
 This is quite slow, on average half the records
need to be read, however if the data exists it
will always be found

19. Searching for data
Second Method: Binary search.
 This method will only work if the data records have been ordered
based on the field in which you intend to search
 The middle record is located and the contents of the field is
compared to the criterion
 If the criterion is less than the middle value, then the search is
limited to the lower half of the data file (vice versa if criterion is
greater then the middle value). The middle record of the lower
half of the data file is located and the above step is repeated
 This continues until a match has been found (or not if there is no
match)
 This is a much faster searching method than the linear search
but has the overhead of maintaining the records in sorted order

20. Indexed Sequential data storage
This uses a main data file and another file called
an index file that contains the primary key for
each record and a pointer for each record
To locate a particular record, the index file is
searched until the required primary key is found
A pointer will direct the search to a particular
location in the main data file for the required
record
There can also be other index files with data
based on another field, along with pointers
This allows for faster data access

21. Hashed file storage
Divides memory up into a number of separate
storage locations and allocates an identifying
number to each storage location
The storage location for each record is found by:
 Dividing the key field value of the record by the
number of storage locations
 The remainder after the division becomes the location
number for that particular record
Very fast processing of data, but complex to
manage

22. Backing Up Data

23. Backup Procedures
A backup is a copy of data files or a file system that is
created in case the original files are damaged or lost
The backup is used to restore the data and in some
cases an entire system
We often create backup “disk images”, files that are
essentially a copy of the entire contents of a computer’s
hard drive
 If a computer fails, the disk image can be copied to the hard
drive of the faulty computer overwriting the damaged hard drive
files
 “ghosting” is a common term for this procedure
 This allows a damaged computer to get back on-line fairly
quickly

24. Grandfather, Father, Son backups
The most recent backup is called the son, the
previous backup is the father and the oldest
backup is the grandfather
When the next backup is due
 The grandfather media will become the son
 The father media will become the grandfather
 The son media will become the father
 And so it continues
The advantage of this method is that it allows data to be
recovered from any one of the last three backup cycles
It is common for damaged data not to be detected until
some time afterwards, hence the advantage of having
the grandfather

25. Partial Backups
Partial backups are a method devised to cut down on the
time it takes to perform a complete backup of data
Essentially only those data files that have been created
or changed since the last backup are stored
There are two types: incremental and differential
Students need to identify the advantages and
disadvantages of each type of back up

26. Incremental partial backup
On each day only those files created or changed since
the previous day’s backup are copied
So, on Monday, if I create a new file and edit another file,
then only those two files will be backed up
Obviously, there is still a need to do a regular complete
backup, but this may be limited to just once a week
Recreating the entire system after a failure occurs,
takes some time as data has to be obtained from the last
complete backup and from all of the partial backups
The OASIS system in school admin used a version of
this method

27. Differential partial backup
Each day, all files that were created or changed since
the last complete backup are copied and saved
So, Monday’s backup would contain changes made on
just Monday
Tuesday’s backup would contain changes made on
Monday and Tuesday
Wednesday’s backup would contain changes made on
Monday, Tuesday and Wednesday. etc
Recreating the entire file system would be a lot quicker
because all you would need to do is load files from the
last complete backup and the last partial backup

28. Output from a TPS

29. Output from a TPS
The role of the TPS is to organise data so that it
can be used by other systems, such as:
 Management Information Systems – used to report on
the current status of an organisation. It uses data
such as product sales, monthly sales reports etc, all
provided by the TPS, to help managers identify areas
of concern
 Decision Support Systems – help managers to make
decisions. We shall learn more about these soon

30. Social and Ethical Issues
There are some fairly critical issues
related to the use of TPS. These include:
 Data security
 Safeguards against systems failure
 Data bias
 Data Integrity

31. Activities
It is difficult to find practical activities for TPS
While the students handle the theory well, they
may be unhappy that the topic is so theoretical
There are any number of businesses that would
make good excursion venues to see transaction
processing systems in action, though access to
their IT section may be difficult to arrange. Some
students may have parents in business that
would be more cooperative in this regard

32. Activities
Ware, Chelesiki and Chivers’ book has a good major
project idea based on TPS
It involves the use of data loggers to measure and store
data on a number of environment conditions
The students design and implement a TPS to process
the data gathered by the loggers
Apparently, data loggers are a requirement of the HSC
Science courses, so “…they should be in every school.”
Its not a bad activity, however, you may have to spend
some time determining how the data loggers work
Alternatively, ‘live’ data can be obtained from numerous
stations around the world via the internet

33. Activities
Use of relational databases. If you are
able to you could extend the students
capabilities using Microsoft Access or
FileMaker Pro to simulate a TPS e.g. a
supermarket checkout and stock control
system

34. The end