Queue Manager Manual

Application Development Steps
Developing Queue Manager Applications
3–2 46517 Tandem Computers Incorporated
Step 2: Specifying the
Functional Aspects
Identify the entities that will request work of each other or of other processes.
Consider whether these entities are people, processes, devices, or other entities; your
application must interface with each of these types differently.
Consider how many entities your application will involve and how they will interact.
Determine which users or processes will be requesters and which will be servers. Be
aware that servers frequently become requesters when they have completed work on
an item and pass it on to another process. Decide the action each server will take, such
as adding information to a work item or returning it to the Queue for another process
to process further. Define the characteristics of the UOWs that processes exchange.
Consider factors such as:
What kind of information does each work request contain? Queue Manager is
indifferent to UOW content, allowing applications to define Queue entry data for
their own purposes.
Is the order in which work requests are processed important? Your application
can embed priority information inside Queue entries and provide process code to
process entries in priority sequence.
Is the time window in which entries will be enqueued a consideration? This might
involve distinguishing between servers that are batch applications running only at
night and online processes active during the day. It might also require careful
analysis of the daily availability of devices that are recipients of work requests.
How do the servers use entry information?
Do the servers need to confirm successful dequeuing of an entry? Some requesters
might demand a response from the server. This would create another instance
where a server would become a requester, by enqueuing a confirmation entry on
the Queue for dequeuing by the original requester process.
Consider whether confirmations will be more useful or more annoying to the
sender process and whether the need for confirmation warrants the additional
system traffic and I/O.
In addition to UOW content, consider the level of data protection and integrity your
application must provide based on the criticality of the functions defined. Such
requirements might involve the use of fault-tolerant features, TMF, or both.
Try to anticipate any operational and administrative requirements that your
application imposes upon others at your site.
Step 3: Designing Input
Screens
If your application involves users at terminals, design the input screens and establish
conventions for reporting errors.
Determine what screens are needed, how the screens should be grouped, and what
path the user should take while progressing through particular screen sequences.
As an example:
The application presents a user with a logon screen.