Queue Manager Manual

3 Developing Queue Manager
Applications
46517 Tandem Computers Incorporated 3–1
An application can be designed and developed in many different ways. As a general
guideline, Tandem suggests the following combination of steps as one possible way to
proceed:
Decide whether your application should use Queue Manager.
Specify the functional aspects of the application. Identify the users or programs
involved and what they do, what kind of information they exchange, how they use
that information, and whether they acknowledge receipt.
Design input screens for users at terminals.
Divide the application tasks among requesters, servers, and other processes and
programs.
Define the UOW data content.
Plan high-level transactions, taking TMF requirements into consideration.
Plan low-level implementation.
Code and test the software.
Application
Development Steps
The application development steps presented in this section are only guidelines that
suggest an approach; they do not imply design prerequisites or a rigid methodology.
Statements about what different entities, such as requesters and servers, should do are
simply ideas that offer one model of how Queue Manager can be used.
A complete listing of an example of a Queue Manager application written in COBOL
appears in Appendix B.
Step 1: Deciding Whether
to Use Queue Manager
Consider using Queue Manager if your application requires separating activities into
multiple stages or feeding many work requests to a central server. These requirements
need not be the primary thrust of the application; even if they are only a small part of
it, Queue Manager can still help you considerably as a buffer between requesters and
servers.
Queue Manager is not an application in itself. Rather, it allows requesters and servers
to process asynchronously. Queue Manager ensures that a requester's work entry will
remain safe on a Queue protected by TMF until the server is ready to take the work off
the Queue. The server does not have to satisfy the request immediately.
The Wait Manager may be the key Queue Manager function to consider in planning an
application. By notifying servers when an entry of interest arrives,Wait Manager saves
these processes having to read the Queue periodically for work items. Thus, Queue
Manager can be effective not only in buffering servers from a flood of work requests,
but also in supporting applications for which work items appear only rarely. With
Queue Manager waiting for the entries to appear, servers can do other things and
avoid useless I/O on the Queue file.