Modes of Processing

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Modes of Processing
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Definition - transaction

• All data processing systems are concerned with
  transactions events that need to be recorded
• Examples could include
• Buying a product in a shop
• Withdrawing cash from an ATM
• Booking a cinema ticket
• Navigation control on an aeroplane
• Using gas/electricity etc.

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Modes of processing
Three methods are used to process transactions
Real-time
No delay (i.e. instant)

• Real-time
• Transaction
• Batch

Transaction
Short delay
The main difference between them is how soon
after input data is processed.
Batch
At a later time
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Batch Processing 1

• Batch processing is used when there are a large
  number of similar transactions to be processed
• All the data to be processed is collected
  together BEFORE being processed in a single
  operation
• Processing is delayed until a convenient time
  e.g. at night or weekly or monthly
• There is a delay in processing which means the
  master file may not be up-to-date

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Batch Processing 2
Transactions are batched together in an offline
transaction file
The old master file is called the father and the
new master file the son. When the son is used to
create a new master file it becomes the father
and the old father becomes a grandfather. Both
the father and grandfather will be stored for
backup purposes
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The transaction file is sorted into the same
record order as the master file
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Records from the transaction file are merged
with corresponding records in the master file
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Updated records are stored in a new master file
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The cycle is repeated for each record in the
transaction file
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Batch Processing 3

• An example of batch processing is the way that
  credit card companies process billing. The
  customer does not receive a bill for each
  separate credit card purchase but one monthly
  bill for all of that months purchases.

• The bill is created through batch processing,
  where all of the data are collected and held
  until the bill is processed as a batch at the end
  of the billing cycle.

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Transaction Processing 1

• In transaction processing data is entered and
  processed straight away
• However, there may be a short delay as the system
  must COMPLETE each transaction BEFORE starting
  the next one
• Sometimes called interactive or pseudo real-time
  processing i.e. it looks like stuff is
  happening instantly

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Transaction Processing 2

• A common use of interactive processing is for
  booking systems
• Remember, each transaction must be completed
  before the next one begins
• Why does this make interactive processing the
  most appropriate method for booking systems?

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Real-time Processing

• Real-time processing occurs when the system
  responds instantly to events
• Examples include
• Controls on an aeroplane
• Nuclear reactors/power stations
• Computer games

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Choosing a processing mode

• The choice of method will depend on a number of
  factors
• Whether data has to be completely up-to-date at
  all times
• Cost real-time/pseudo real time systems are
  generally more expensive. Why?
• Computer usage. Batch processing can take
  advantage of idle computer time e.g. overnight
• Many systems applications will use a combination
  of batch AND interactive processing.

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Tasks

• Use your textbook/Internet resources to make
  notes on Modes of Processing
• Complete the exercise on pages 187 188 of Mott
  Leeming