Error handling Logic we are using expression transformation to find the data is coming in expected dormat or not suppose date range dd/mm/yyyy from source data loaded like mm/dd/yyyy then its not matching our requirement for the particular date port then its send error message to Error handling target

After validating the incoming source data if we find any invalid data(eg: data not present the dimension table null data or difference in the data format) then it can be loaded to a reject table(include one remark column which will help us to identify the cause of rejection). Rerun the workflow after correcting the data in source based on the cause of rejection.

Bad files contains column indicator and row indicator.
Row indicator: It generally happens when working with update strategy transformation. The writer/target rejects the rows going to the target

Columnindicator:
D -valid
o - overflow
n - null
t - truncate
When the data is with nulls or overflow it will be rejected to write the data to the target
The reject data is stored on reject files. You can check the data and reload the data in to the target using reject reload utility.