How IBM IMS Queue Control Facility for z/OS works

Queue overflow protection

IBM® IMS™ Queue Control Facility for z/OS® implements queue overflow protection by monitoring the message queue usage. It analyzes the message queue usage to determine when to send an alert or to take action to prevent the excessive queue usage from continuing. You can configure queue overflow protection by specifying various parameters to specify partition values, set queue usage limits and specify appropriate alerts and actions.

Message processing

Use IMS Queue Control Facility to process messages from the IMS system log, IMS queue manager message queues as well as shared queues – in a shared queues only environment. Process selected messages based on the criteria that you specify in control statements. IMS Queue Control Facility produces an output data set and a data report that includes quantitative information about the selected messages.

Recovery and maintenance functions

IMS Queue Control Facility helps you perform recovery and maintenance tasks, such as message queue recovery after either a planned or unplanned system outage. It provides application recovery when it is practical to return messages to the message queue for reprocessing. You get IMS maintenance for both shared and nonshared queue environments. It allows you to query, browse, unload, and load IMS messages from, or to, the IMS message queues.

Message requeueing

In the nonshared queue environment, IMS Queue Control Facility gets messages that need to be requeued from the system log data sets (SLDS) or the IMS queue manager message queues. In the shared queue environment, IMS Queue Control Facility gets messages from the cold queue – a special queue for messages that were in process when IMS terminated abnormally and was cold started. Recovery in the shared queues environment only applies to messages on the cold queue.

Queue maintenance

In the shared queues environment, messages that were in process stay on the cold queue and accumulate until you remove them. This accumulation of messages degrades performance and wastes space on the shared queues. In the nonshared queues environment, messages can use enough buffer resource to cause a buffer shortage. A buffer shortage can cause IMS to abnormally terminate with a user 758 abend code.

TSO client/ISPF interface

IMS Queue Control Facility TSO client (ISPF interface) helps you select the server and IMS subsystem to be used. You can view the IMS environment that you are using and your local queue status. It allows you to query messages and list destinations of the queued messages. You can unload messages from the IMS message queues and load or reload messages onto the IMS message queues. You can also maintain the tables that are associated with queue overflow protection for a non-shared queue environment.