Consider the following factors when you process records in UNIX files:

• Block boundaries are not maintained within the file. If you write a short block other than at the end of the file, a later read at that point returns a full block (except for RECFM=VB, which always returns a single record).
• Record boundaries are not maintained within binary files except with fixed-length records, but the access method maintains record boundaries when FILEDATA=TEXT or FILEDATA=RECORD is in effect..
• Text files are presumed to be EBCDIC.
• Repositioning functions (such as POINT, BSP, CLOSE TYPE=T) is not permitted for FIFO or character special files.
• The default record format (DCBRECFM) is U for input and output.
• The default block size (DCBBLKSI) on input is 80. There is no default for output.
• The default LRECL (DCBLRECL) on input is 80. There is no default for output.
• When RECFM=F(B(S))
  • And the file accessed has a FILEDATA type of binary, if the last record in the file is smaller than LRECL bytes, it is padded with zeros when it is read.
  • And the file accessed has a FILEDATA type of text, if any record in the file is smaller than LRECL bytes, it is padded with blanks when it is read. If any record is longer than LRECL bytes, it results in an I/O error due to incorrect length when it is read.
  • And the file accessed has a FILEDATA type of record, if any record in the file is smaller or larger than LRECL bytes, it results in an I/O error due to incorrect length when it is read.
• When RECFM=V(B)
  • And the file accessed has a FILEDATA type of binary, each record is returned as length LRECL, except, possibly, for the last one.
  • And the file accessed has a FILEDATA type of text, if any record in the file consists of zero bytes (that is, a text delimiter is followed by another text delimiter), the returned record consists of an RDW and no data bytes. If any record is longer than LRECL bytes, it results in an I/O error due to incorrect length when it is read.
  • And the file accessed has a FILEDATA type of record, if any record in the file consists of zero bytes (that is, a record prefix (IGGRPFX) contains a zero length), the returned record consists of an RDW with no data bytes. If any record is longer than LRECL bytes, it results in an I/O error due to incorrect length when it is read.
• When RECFM=U
  • And the file accessed has a FILEDATA type of binary, each record is returned with a length equal to block size, except, possibly, for the last one.
  • And the fileaccessed has a FILEDATA type of text , if any record in the file consists of zero bytes (that is, a text delimiter is followed by another text delimiter), the returned record consists of one blank. If any record is longer than the block size, it results in an I/O error due to incorrect length when it is read.
  • And the file accessed has a FILEDATA type of record, if any record in the file consists of zero bytes (that is, a record prefix (IGGRPFX) contains a zero length) or any record is longer than BLKSIZE bytes, it results in an I/O error due to incorrect length when it is read.