Using ENF event code 67 to listen for IBM Health Checker for z/OS availability

If your remote check is authorized, it can use the ENFREQ LISTEN service to see when IBM® Health Checker for z/OS® is up and running, or whether a check's status has changed. On the ENFREQ service, you specify the specific event for which you would like to listen (IBM Health Checker for z/OS availability) and the listener user exit routine that is to receive control after the specified event occurs. The listener user exit specified receives control when IBM Health Checker for z/OS comes up and notifies the remote check routine, which can then define itself using HZSADDCK.

To listen for ENF event code 67, you must specify the qualifying events on the BITQUAL parameter, which specifies a 32-byte field, a hexadecimal constant, or a register containing the address of a 32-byte field containing a bit-mapped qualifier that further defines the event. The qualifiers are mapped by mapping macro HZSZENF. The defined BITQUAL values are:

Qualifier

Information type

X'80000000'

IBM Health Checker for z/OS is available. Field Enf067_BitQual_Available in the HZSZENF mapping macro.

X'40000000'

IBM Health Checker for z/OS has terminated and is not available. Field Enf067_BitQual_NotAvailable in the HZSZENF mapping macro.

X'20000000'

The status has changed for a check. Field Enf067_BitQual_StatusChange in the HZSZENF mapping macro. This might mean:

The check completed with a different result than the last time it ran. For example, the check ran successfully after the previous check run issued an exception or vice versa.
The check was deactivated or deleted

If you are monitoring this event, upon receiving this you would probably want to issue the HZSQUERY macro to get information about the check.

This event may not be presented if IBM Health Checker for z/OS is terminating (indicated by a X'40000000' ENF 067 event for NotAvailable).

Note that it is possible that IBM Health Checker for z/OS will not be up any longer by the time the check routine issues the HZSADDCK routine to define the check to the system. In this case, if the check was using ENFREQ to LISTEN, it should return to listening again. If the check was periodically re-trying the HZSADDCK macro, it should go on trying.

If the check routine decides it is no longer interested in knowing if IBM Health Checker for z/OS is up or not, it can issue the ENFREQ REQUEST=DELETE request to delete the listen request.

For information about ENFREQ and listener exits, see: