When there is a problem with INDEX, CHECK INDEX will tell you what is wrong with INDEX, and the relevant index key and RID information will be listed in REPORT.
Take a look at check index output:
DSNU708I tells us that the index key '00C1' on RID 202 is not unique
DSNU713I tells us that the value of the key column on the index is '00C1', and the corresponding value on the data record is '00C2'. .