BTAM is a block-oriented access method, i.e. BTAM does not recognize any record structures within blocks. BTAM therefore interprets the input RECFORM=F in the FILE macro or RECORD-FORMAT=*FIXED in the ADD-FILE-LINK command to mean that all the blocks in this file have a fixed block size.
BTAM supports the following record formats:
F for fixed-length records
U for records of undefined length
V for variable-length records (formats V and U are treated identically)
BTAM only processes files with the format BLKCTRL=NO or BLOCK-CONTROL-INFO=*NO.
If RECFORM=U or RECORD-FORMAT=*UNDEFINED is specified, DMS takes the block size
from the register defined with RECSIZE=reg in the FILE/FCB macro
from the specification in the action macro (LEN operand)
from the specification in the RECORD-SIZE operand of the ADD-FILE-LINK command
If RECFORM=F or RECORD-FORMAT=*FIXED is specified, the block size defined by BLKSIZE or RECORD-SIZE or specified in the LEN operand of the BTAM macro is used.
The block size may be: 18 bytes <= block size <= 32768 bytes.
Files created with SAM can be processed with BTAM. Each user, however, is then responsible for unblocking the records.