Making global online changes in a sysplex that uses XRF

The XRF alternate does not participate directly in a global online change. The alternate participates indirectly once it receives the X'70' and X'22' log record written by the XRF active system.

The QUERY MEMBER command might show some online change status for the XRF alternate while it is processing the X'70' and X'22' log record.

During takeover of an active system, the XRF alternate updates the OLCSTAT data set with its IMSID. After the takeover is complete, the XRF alternate behaves like any IMS active system and can participate in a global online change. The abended XRF active system can be brought back up as the new XRF alternate, if desired.

The MODSTAT and MODSTAT2 data sets are not used. You can leave the MODSTAT and MODSTAT2 data set DD statements in your IMS control region JCL, but they are ignored.

Global online change in an XRF environment has the following limitations:

• If an XRF active system fails or is shut down (/SWITCH SYSTEM ACTIVE or /CHE FREEZE) and the XRF alternate system takes over, IMS deletes the IMSID of the failed or shut down XRF active system from the OLCSTAT data set during takeover processing, so that global online change can work even if the old active is down. After takeover, if you bring up the failed or shut down XRF active system as the new XRF alternate system, and initiate global online change, the new XRF alternate system does not process the online change command directly, but performs the online change later when it detects the online change log record.
• If the XRF active system fails and the XRF alternate system attempts to take over before it catches up with the XRF active system's global online change state, the XRF alternate system abends with U2801 RC=X'0011'. The XRF alternate is not synchronized with the OLCSTAT data set. Because other IMS systems in the IMSplex might be synchronized with the OLCSTAT data set, the XRF alternate is not permitted to takeover.