Flushes trace data and operational messages to the //XDBOUT DD SYSOUT data set. Operational data is written to XDBOUT during normal operation; trace data is written to XDBOUT only when tracing is switched on and the trace destination is SYSPRINT. The FLUSH command causes any partially filled buffer to be written to the SYSOUT data set, making the output available for browsing. This can be helpful when you are testing and trying to view trace data interactively as the test progresses.
Here is an example of a FLUSH XDBOUT command and the response:
F MFA,FLUSH XDBOUT MFM0015I: Flush XDBOUT completed