Specify how to divide the application into transactions.
Procedure
- Name each transaction, and describe its function in terms
that the terminal user can understand. Your application
could include transactions to recover from failures, such as:
- Progress transaction, to check on progress through the
application. Such a function could be used after a transaction failure
or after an emergency restart, as well as at any time during normal
operation. For example, it could be designed to find the correct restart
point at which the terminal user should recommence the interrupted
work. This would be particularly relevant in a pseudo-conversation.
- Catch-up function, for entering data that the user might
have been forced to accumulate by other means during a system failure.
- Specify the files and databases that can be accessed in
each processing unit. Of the files and databases that can
be accessed, specify those that are to be updated as distinct from
those that are only to be read.
- Specify how to apply the updates for those files and databases
that can be updated by an application processing unit. Factors
to consider here include the consistency and the immediacy of updates.
- Specify which, if any, updates must happen in step with
each other to ensure integrity of data. For example,
in an order-entry application, it might be necessary to ensure that
a quantity subtracted from the inventory file is, at the same time,
added to the to-be-shipped file.
- Specify when newly entered data must or can be applied
to the files or databases:
- The application processing unit updates the files and databases
as soon as the data is accepted from the user.
- The application processing unit accumulates updates for later
action; for example, by a later processing unit within the same application
or a batch application that runs overnight. If you choose the batch
option, make sure that there is enough time for the batch work to
complete the number of updates.
Use this information when deciding on the internal design
of application processing units.
- Specify what data needs to be passed from one application
processing unit to another. For example, in an order-entry
application, one processing unit might accumulate order items. Another
separate processing unit might update the inventory file. Clearly,
there is a need here for the data accumulated by the first processing
unit to be passed to the second. Use this information
when deciding what resources are required by each processing unit.