Options for Detecting a List or Event Queue Transition

You can detect list or event queue transitions two different ways:

By having your list notification exit receive control when the list or event queue changes from empty to nonempty. Your list notification exit then invokes the IXLVECTR macro to check the state (empty or nonempty) of each list or event queue you are monitoring.
By coding a polling routine to invoke the IXLVECTR macro periodically to check the state of each list or event queue you are monitoring.

For each list or event queue you monitor, you can choose how you want to detect list or event queue transition. You can monitor some using a list notification exit and others by whatever method you choose, such as polling the list notification vector.