For disk data sets you must have your userid authorized as a high-level index in the catalog and have the necessary access limits specified through RACF. Then if you name your data sets starting with your userid (i.e., userid.file.name), they will be secure. For the tapes, you must name tape files with names less than 17 characters long, but still beginning with your userid. This stops someone from arbitrarily appending some other high-level index to the data set name to gain unauthorized access. Only the last 17 characters of the file name are recorded in the tape label and only these characters are compared when validating access. This effectively puts one or more leading blanks in the label field and prevents anyone from sticking some other prefix on the name. (ras) | 