Using ENF event code 80 to notify applications of TCP/IP joining or leaving a sysplex

ENF event code 80 is used to send signals when a TCP/IP stack in a sysplex environment joins or leaves a sysplex group for any reason. Authorized applications can use the ENFREQ LISTEN service to detect ENF events. On the ENFREQ service, specify the LISTEN action, the 80 event code, the X'40000000' event qualifier, and the listener user exit routine that is to receive control after the specified event occurs. The specified listener user exit receives control when the TCP/IP stack completes its join or leave.

To listen for ENF event code 80, specify the qualifying event on the QUAL parameter in one of the following forms:

A 4-byte hex value (X'40000000')
A constant containing a 4-byte hex value

The qualifier is mapped by the mapping macro EZAENF80. The QUAL value for the status change event is ENF80_SYSPLEX_EVENT in EZAENF80. The EZAENF80 macro is in SYS1.MACLIB. See EZAENF80 Parameter list for ENF event code 80 listen exits for the mapping of ENF80 and ENF80_SYSPLEX control blocks.

When the listener user exit is driven, the ENF80 and ENF80_SYSPLEX control blocks are provided. The exit can use ENF80_SYSPLEX_FLAGS to determine whether the TCP/IP stack is joining or leaving a sysplex group. The job name of the TCP/IP stack is also provided.

If ENF80_SYSPLEX_JOIN is on, the TCP/IP stack is joining the sysplex group. The application can form connections with this stack.
If ENF80_SYSPLEX_LEAVE is on, the TCP/IP stack is leaving the sysplex group. The application can clean up DVIPA that were previously in use.

If the application does not need to know whether the TCP/IP stack is in the sysplex group, issue the ENFREQ REQUEST=DELETE request to delete the listen request.

For information about ENFREQ and listener exits, see the following references: