The server sends this reply when it receives a SIZE command while SBSENDEOL is not set to CRLF. FTP cannot reliably calculate the file transfer size when the SBSENDEOL setting is not CRLF.
The SIZE command is rejected.
If you want to change the setting of SBSENDEOL for this session, use the SITE SBSENDEOL=value subcommand. See the SIte subcommand in z/OS Communications Server: IP User's Guide and Commands for more information. If you continue to experience this error, report the error to the system programmer.
Most clients do not require or tolerate an SBSENDEOL setting other than CRLF. If your users require the alternate server SBSENDEOL setting only for certain file transfers, code SBSENDEOL CRLF in the server's FTP.DATA and instruct your users to send a SITE SBSENDEOL command to the server just before those file transfers. The server will accept the SIZE command until the SBSENDEOL value is reset.
The SIZE command is often part of a sequence of commands sent by the FTP client to restart a file transfer while in stream mode. If your users often need to restart file transfers, consider whether block or compressed mode transfers would be appropriate for your installation. Block and compressed mode transfers can be restarted provided you have initiated checkpointing before the file transfer. See the information about restarting a failed data transfer in z/OS Communications Server: IP User's Guide and Commands for more information.