FILE
Specifies the name of the output file.
The FLUSH statement flushes the buffers associated with an open output file (or with all open output files if * is specified). This normally happens when the file is closed or the program ends, but the FLUSH statement ensures the buffers are flushed before any other processing occurs.
You can do this for SYSPRINT (after a PUT DATA) to make the output immediately visible in, for example, SDSF.