The stdin, stdout, and stderr I/O destinations (SYS$INPUT, SYS$OUTPUT, and SYS$ERROR) are all controlled by PMDF and will vary depending upon the context under which a channel program has been invoked. As such, programs which will operate as PMDF channels should use the PMDFlog routine to write information to their log file. Such programs should never write output directly to stdout or stderr or other generic I/O destinations (e.g., Pascal's "output" or FORTRAN's default output logical unit). There's no telling where such output might go: it might go to the job controller's log file, it might even go down a network pipe to a remote client or server.

Note that the channel log file is a different file than the PMDF log file; the PMDFlog and PMDFcloseLogFile are unrelated routines.