In this post, you’ll learn about the COBOL runtime Error Code 066 and the reason why you are receiving it
COBOL Error Code :
066
Reason for this Error in COBOL
Attempt to add duplicate record key to indexed file (Fatal) -You have tried to add a duplicate key for a key which you have not defined as being able to have duplicates. -As this error implies that your program logic contains a mistake, you probably should recode.