You can partially rename all fields in an externally described file by using the PREFIX keyword on the file-description specification for the file. You can either add a prefix to the existing field name or you can replace part of the existing field name with a sequence of characters. The format is PREFIX(prefix-string: {nbr_of_char_replaced}). Figure 158 shows some examples of the use of PREFIX.
*.. 1 ...+... 2 ...+... 3 ...+... 4 ...+... 5 ...+... 6 ...+... 7 ...+... *
FFilename++IPEASFRlen+LKlen+AIDevice+.Keywords+++++++++++++++++++++++++++++
* Add the prefix MST to each name in the record format
FITMMSTL IP E K DISK PREFIX(MST)
*
* Change the prefix YTD to YE for each name in the record format
FSALESMSTR IP E K DISK PREFIX(YE:3)