How to Assign Priorities to Interfaces or Services


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Assigning priorities enables you to exert significant control over the flow of data in an application, provide faster service to the most important requests, and provide slower service to the less important requests. You can also give priority to specific users—at all times or in specific circumstances.

You can assign priorities to BEA Tuxedo services in either of two ways:

Administratively—in the SERVICES section of the configuration file, specify the PRIO parameter for each service named.
Programmatically—add calls to the tpsprio() function to the appropriate client and server applications, to allow designated clients and servers to change a priority dynamically. Only preferred clients should be able to increase the service priority. In a system on which servers perform service requests, the server can call tpsprio() to increase the priority of its interface or service calls so the user does not wait in line for every interface or service request that is required.

Example of Using Priorities

Server 1 offers Interfaces A, B, and C. Interfaces A and B have a priority of 50; Interface C, a priority of 70. An interface requested for C is always dequeued before a request for A or B. Requests for A and B are dequeued equally with respect to one another. The system dequeues every tenth request in first-in, first-out (FIFO) order to prevent a message from waiting indefinitely on the queue.

Using the PRIO Parameter to Enhance Performance

The PRIO parameter determines the priority of an interface or a service on a server's queue. It should be used cautiously. Once priorities are assigned, it may take longer for some messages to be dequeued. Depending on the order of messages on the queue (for example, A, B, and C), some (such as A and B) are dequeued only one in ten times when there are more than 10 requests for C. This means reduced performance and potential slow turnaround time for some services.

When you are deciding whether to use the PRIO parameter, keep the following implications in mind:

Because higher priorities get first preference, a higher priority should usually be assigned only to an interface or service that is not called frequently.
A message with a lower priority does not remain enqueued indefinitely; every tenth message is retrieved on a FIFO basis. Before you assign a low priority to an interface or service you should be sure that response time for that interface or service is not important.