The messages in a service-controlled queue must be retrieved by a service of the application before they can be processed. In other words, the initiative must always come from a service of the application, since openUTM does not take on any triggering functionality for these queues.
openUTM provides three types of service-controlled queues:
USER queues:
A USER queue is user-specific and available automatically to every UTM user.TAC queues:
These queues are available in principle to every service. They have a fixed name that has to be generated explicitly. An exception is the dead letter queue, which is permanently named KDCDLETQ and which does not have to be generated.Temporary queues:
A temporary queue is generated and deleted again dynamically by a service by means of a program call.
openUTM supports both the browse and the processing function for all service-controlled queues:
Browse
The message can be read by several services in parallel and remains in the queue after it has been read.Process
The message can be read only by one service at a time and is deleted after it has been read.
Both service-controlled queues and UTM-controlled queues are subject to the openUTM transaction concept.
The messages are queued with transaction management and remain there, fault-tolerant, until they are retrieved with transaction management by the services and further processed.
If a transaction is rolled back, the messages processed in the transaction are placed back in the queue and can be read again (redelivery). Alternatively, or after the last redelivery attempt, openUTM can put the incorrectly processed FGET message of a TAC queue in the dead letter queue.
| You can set the maximum number of redeliveries after a transaction rollback. Details are available in the openUTM manual “Generating Applications”, keyword REDELIVERY. |
