There are just two positional parameters in the JCL JOB statement: the "accounting" parameter and the programmer name parameter. The "accounting" parameter used to contain a number of positional parameters in JES2. I've long since forgotten all of them, and most of them can be specified as keywords in the /*JOBPARM JECL statement. The first few are account number, room ID, max lines in thousands of lines, max cards, ... All of them are limited to 4 characters. I presume that's what you are refering to.