WebSphere Application Server V7.0: Concepts ... - IBM Redbooks

Exploitation of XCF techniques
WebSphere Application Server for z/OS uses the XCF communication, which
offers three different services:
► Group services
► Signaling services
► Status monitoring services
Only the group service is used for the XCF support for WebSphere HA manager.
To use the XCF system service, WebSphere Application Server for z/OS V7.0
provides an XCF plug-in that contains XCF user routines, as shown in
Figure 14-8 on page 442.
Become a XCF group member
When the XCF-based protocol is configured as the discovery and failure
detection protocol, then for each WebSphere Application Server core group one
XCF group will be created and the core group members will become active
members of this XCF group.
To become an active member of a XCF group, during startup of a core group
member (for example a node agent) the IXCJOIN macro is executed. As a result
the member is associated with the address space in which the IXCJOIN was
issued and added to the XCF group. As an active XCF member, it can perform
the following tasks:
► Send and receive messages to other members
► Have its status monitored by XCF
► Be notified of status changes to other members of the group
Each WebSphere Application Server component that can become a core group
member can become a XCF group member.
Status change
The XCF group service has three options of recognizing that a member is no
longer active:
► The corresponding XCF macro is run that disassociates a member from the
XCF group. This happens when the core group member is stopped through
the Integrated Solutions Console.
► The address space (with the core group member in it) that is associated with
the XCF member is terminated. This will result in the termination of the XCF
member.
► The status user routine of the XCF member (and the core group member) is
no longer working. To show that a member is still running, it needs to update a
specific field. If the member fails to update this field within a specified time
interval, XCF schedules the status user routine to determine if a problem
exists.
Chapter 14. WebSphere Application Server for z/OS 443