Fixed-format records
These are the formats you can specify for RECFM if you want to
use a fixed-format file:
- F
- Fixed-length, unblocked
- FA
- Fixed-length, ASA print-control characters
- FB
- Fixed-length, blocked
- FM
- Fixed-length, machine print-control codes
- FS
- Fixed-length, unblocked, standard
- FBA
- Fixed-length, blocked, ASA print-control characters
- FBM
- Fixed-length, blocked, machine print-control codes
- FBS
- Fixed-length, blocked, standard
- FSA
- Fixed-length, unblocked, standard, ASA print-control characters
- FSM
- Fixed-length, unblocked, standard, machine print-control codes
- FBSM
- Fixed-length, blocked, standard, machine print-control codes
- FBSA
- Fixed-length, blocked, standard, ASA print-control characters.
In general, all references to files with record format FB also
refer to FBM and FBA. The specific behavior
of ASA files (such as FBA) is explained in Using ASA text files.
Attention: z/OS® XL C/C++ distinguishes between FB and FBS formats,
because an FBS file contains no embedded short blocks (the
last block may be short). FBS files give you much better
performance. The
use of standard (S) blocks optimizes the sequential processing
of a file on a direct-access device. With a standard format file,
the file pointer can be directly repositioned by calculating the exact
position in that file of a given record rather than reading through
the entire file.
If the records are FB, some blocks may contain fewer records than others, as shown in Figure 1.
Figure 1. Blocking fixed-length records