Understanding the service timer

Queue service interval events use an internal timer, called the service timer, which is controlled by the queue manager. The service timer is used only if one or other of the queue service interval events is enabled.

What precisely does the service timer measure?

The service timer measures the elapsed time between an MQPUT call to an empty queue or a get operation, and the next put or get, provided the queue depth is nonzero between these two operations.

When is the service timer active?

The service timer is always active (running), if the queue has messages on it (depth is nonzero) and a queue service interval event is enabled. If the queue becomes empty (queue depth zero), the timer is put into an OFF state, to be restarted on the next put.

When is the service timer reset?

The service timer is always reset after a get operation. It is also reset by an MQPUT call to an empty queue. However, it is not necessarily reset on a queue service interval event.

How is the service timer used?

Following a get operation or an MQPUT call, the queue manager compares the elapsed time as measured by the service timer, with the user-defined service interval. The result of this comparison is that:

• An OK event is generated if there is a get operation and the elapsed time is less than or equal to the service interval, AND this event is enabled.

• A high event is generated if the elapsed time is greater than the service interval, AND this event is enabled.

Can applications read the service timer?

No, the service timer is an internal timer that is not available to applications.

What about the TimeSinceReset parameter?

The TimeSinceReset parameter is returned as part of the event statistics in the event data. It specifies the time between successive queue service interval events, unless the event statistics are reset.