Notifying other VTAMs of the takeover in XRF with USERVAR

During takeover, if Extended Recovery Facility (XRF) with USERVAR is used, the alternate subsystem issues a MODIFY USERVAR command to change the VTAM® application name in its USERVAR table. If you are using VTAM Release 3.1 or an earlier release, network operators in all VTAM domains except the one for the alternate subsystem, including the failed active, must change these entries. The network operators for each of these VTAM instances issue the same command.

When an entry in the USERVAR table changes, VTAM responds with this message:

IST813I USERVAR IMS CHANGED FROM name1 TO name2

Until the USERVAR is changed for these VTAM nodes, terminals owned by those VTAM instances cannot log on to the new active subsystem.

You might want your operator to delay issuing this command after a takeover until processing on the new active subsystem stabilizes. In fact, if the processing environment for the new active subsystem is inferior to that at the failed active subsystem, you might not want any more terminals to connect to the new active subsystem.

If your installation has installed Tivoli® NetView for z/OS®, you can use Tivoli NetView for z/OS to communicate the new application name.