The binary processing mode specifies to send and receive file contents between the z/OS host and the client in binary form, avoiding the ASCII/EBCDIC conversion required in text mode. This is faster than text mode. However, users on MVS cannot read the file, because the contents are not in EBCDIC. Therefore, use the binary processing mode to create or access a file only if the file is not intended to be shared with users on the z/OS host, or the file content is binary.

When fixed-length records are written in binary mode, the server pads the last record of the file with null characters if the last record is less than the fixed record length. These padding bytes are counted in the file size.