The file you need to change is YALCVNMRFP in the model library. This has the prefixes for files (FIL), formats (FMT), functions (MSG) and each field type. If you use ywrkf to work with this file, you should see the record for the field type you are having a problem with. My instructions say to delete the record, and Synon will recreate it starting at AA again. - Bob