This parameter is referred to as group_name by the OS/390 TCP/IP DNS documentation. It is the generic name of a cluster of equivalent server applications in a sysplex. It is also the name within the sysplex domain that clients use to access the CICS TCPIPSERVICE.
More than one TCPIPSERVICE is allowed to specify the same group name.
The register call is made to WLM when the first service with this group name specified is opened. Subsequent services with the same group name do not cause more register calls to be made.
The deregister action is dictated by the GRPCRITICAL attribute, as described below. It is also possible to explicitly deregister CICS from a group by issuing the master terminal (CEMT) or EXEC CICS command SET TCPIPSERVICE DNSSTATUS DEREGISTERED, or by using the equivalent CICSPlex SM command.
The default is NO, allowing two or more services in the same group to fail independently and CICS still to remain registered to the group. Only when the last service in a group is closed is the deregister call made to WLM, if it has not already been done so explicitly.
Multiple services with the same group name can have different grpcritical settings. The services specifying GRPCRITICAL(NO) can be closed or fail without causing a deregister. If a service with GRPCRITICAL(YES) is closed or fails, the group is deregistered from WLM.
The nameserver must be configured to allow it to look up and resolve the generic host name.