Applications that executed successfully under prior releases may issue DUPLICATE FIELD NAME errors when executed under Release 15.0.
Field names must always be unique within any single File Definition and duplicates within an FD have always been trapped. Field names that are unique within an FD, but duplicate across files are not a problem when they occur in master or coordinated files because the field names are qualified with prefixes to specify which file is intended.
However, when field names are duplicated in multiple FDs that are used for Working Storage or Linkage Section, there is no way for the product to tell which FD the user intended for the field. Unpredictable results occur. This shortcoming was discovered and corrected with a PTF in release 14.0 and subsequently fixed in release 15.0 source. Now when duplicate field names are encountered in Working Storage or Linkage Section FDs, MK4PN02 DUPLICATE FIELD NAME errors are generated to make the user aware of the conflict.
There are multiple solutions, but the best is to modify the FD so the field names are unique.
If this cannot be done, Restricted System Modifications 142 and 143 have been developed which allow release 15.0 to function as before, but because of the danger of unpredictable results, resorting to these is discouraged.