With OS/390® Release 8 and higher (as well as Releases 3 through 7 with APAR OW20623 installed), XES provides support for monitoring responses for certain structure rebuild, User Sync Point, and Disconnected or Failed Connection events. This support is intended to limit the extent of potential hang conditions when connectors do not provide an expected response to an event by notifying the operator or an automation package so that some action can be taken against the non-responding connector. When a specific response is not provided within a predetermined time limit, XES issues a message for each connector owing an expected response that is overdue indicating a connector's failure to confirm an event. The messages identify the connector with the outstanding response so that action can be taken. The action, which could be either automated or operator-initiated, could involve gathering connection diagnostic information about the unresponsive connector instance, cancelling the connector, which in turn, would allow the application or subsystem to continue processing.

Installations should be aware that an expected response that is not received in a timely manner does not necessarily indicate that the connector is hung, but could mean that because of environmental conditions, the connector is simply taking a long time to respond. It is highly recommended that before cancelling the connector, the system programmer, operator, or automation program used for message handling, should examine some diagnostic data to confirm that the connector truly is hung.

Events Monitored by XES lists the events for which XES monitoring is in effect.