Look up the return code and reason code to determine why the z/OS UNIX callable service open (BPX1OPN) failed. Examine either the TSO/E ALLOCATE commands, JCL DD statements, or dynamic allocation that defined STDERR, STDENV, STDOUT, or STDPARM. A PATH that does not exist may have been specified or you may not have authorization to access the file. Authorization failure may have been caused by specifying OCREAT without specifying PATHMODE. If a file path was not specified, verify that the default file path /dev/null exists.