I/O error handling

While the active CICS® region can write its surveillance signals successfully to either the XRF control data set or the XRF message data set, it keeps running in spite of I/O errors. However, if the active CICS region has an I/O error while writing a message to the XRF message data set, the alternate CICS region cannot function correctly, so the active CICS region disables it to prevent it from taking over. If the active CICS region is unable to write to either the XRF control data set or the XRF message data set, it can neither disable the alternate CICS region nor keep it properly synchronized, and so the active CICS region fails.

While an alternate CICS region can receive the active CICS region’s surveillance signals and tracking messages successfully, in addition to writing its own surveillance signals to either the XRF control data set or the XRF message data set, it keeps running in spite of some types of I/O error. However, an isolated I/O error that would have no effect during tracking, may cause failure of the alternate CICS region if it occurs during takeover.

Note:
When the active and alternate CICS regions are running in different MVS™ images, they are not necessarily affected in the same way by the failure of a control unit or channel path that provides access to an CAVM XRF data set.
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