If the RECFM of your input data set is FA, FBA, FBM, FM, VA, VBA, VBM, or VM, the data contains a control character at the beginning of the record (after the RDW for variable-length records). This one-byte control character controls printing actions like starting a new line or a new page; it is not part of the record’s data.
When working with this type of source data, you will need to “drop” one byte from the beginning of your record layout. The easiest way to do this is to build the record layout using the positions specified in the mainframe sort control statements and then shorten the first field by one byte. If your records are variable-length, you will need to drop an additional four bytes (for a total of five); see Work with Variable-Length Records.