In these cases, APPC/MVS stops all active traces for the data set (or, for more global errors, all traces for all data sets), and rejects any subsequent ATBTRACE requests for the affected data set (or system). APPC/MVS also does not write any backlog of entries, so all outstanding data is lost. In fact, for I/O errors, the trace entries in the data set might be unusable.

Whenever possible, APPC/MVS writes a trace entry to indicate that it has stopped trace activity, and also notifies the operator by issuing a message to the console. Depending on the error that occurred, you might not find such an entry in the data set you're using, and the usual STOP entry won't appear either. To determine the end of the most recent trace entries, scan through the time stamps on the entry. If wrapping occurred, older trace entries appear after recent entries; otherwise, the most recent entries are at the end of the data set.