DFS2864I EXTERNAL TRACE DATA SET `xxxxxxxx` FULL - SWITCHING TO `yyyyyyyy`.

Explanation

Disk data set xxxxxxxx is full, and IMS is switching to the data set yyyyyyyy.

Programmer response

If the data on the full data set is wanted, it must be copied to another data set or printed. As soon as data set yyyyyyyy is full, IMS switches back to data set xxxxxxxx.