4.6 Report Data File Layout
- All interchange files are of fixed length records.
- All interchange files are sequential files. There are two categories of records: detail and control records.
Detail records contain user information. A record checksum is calculated for each detail record by summing the data contents of essential numeric fields. It is calculated by the sender and checked by the receiver. Control headers contain information such as participant ID, file name, etc., relevant to the file as a whole. Control trailers further protect the file using record counts and hash totals. Should there be any inconsistency in the record checksums, record counts or hash totals, the whole file will be discarded. Different types of records are indicated by the first byte in the records.
- The maximum length of a hash total is confined to the maximum of 18 digits. The implied decimal point of a numeric field, as well as the sign, if any, is ignored. Should overflow occur, the leading digit will be discarded.