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Unformatted text preview: equential processing precludes the possibility of up-to-the-minute data.
4. Sequential processing requires the files to be sorted before processing. That
is, both the transaction and master files must be sorted and placed in the same
sequence prior to processing.
5. Sequential processing often leads to data redundancy problem, since the same
data may be stored in several files sequenced on different .keys.
Many applications require up-to-the-minute timeliness of data. The users of such
applications cannot afford to wait for the transactions to be accumulated in batches
and then processed together. Such applications require a transaction to be
processed immediately as and when it occurs. A few examples of such
applications are airline or railway reservation systems, teller facility in banking
applications, systems for enquiring whether a certain item is in stock in a store,
etc. Note that the activity ratio is very low in these applications since only one
transaction is processed at a time. Hence the use of sequential files for such
applications proves to be very inefficient and uneconomical. The use of
direct/random files is recommended for such applications because in a
direct/random file organization, the desired record pertaining to the current
transaction at hand can be directly located by its key field value without having to
search through a sequence of other records. For example, when a passenger makes
a reservation request for a particular train on a particular date, the computer can
directly access the record for the train and update its seats position for that date.
Obviously, direct/random files need to be stored on a direct access storage device
to enable direct access of records. The principal storage medium for direct/random
files is magnetic/optical disk.
The obvious question that arises now is how are the records in a direct file
physically organized so that it becomes possible to directly access a particular
record, given its key field value, from a number of records store...
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This document was uploaded on 04/07/2014.
- Spring '14