If the FTP-SFTP conversion or the scpg3 and sftpg3 clients are mainly used for file transfers to or from z/OS hosts, and you want to enable direct MVS dataset access on the server side, you need to activate extended streaming by defining SSH_SFTP_STREAMING_MODE=EXT as an environment variable. The traditional SFTP protocol or basic streaming cannot be used, because they require staging.

Also checksums cannot be used in connections to z/OS hosts, because checksum calculation requires staging, and then also the file transfers use staging. Deactivate the checksum mode by defining SSH_SFTP_CHECKSUM_MODE=no as an environment variable.

Use the extended streaming only in connections to z/OS hosts, as it can slow down the transfer of small files in other environments.

For information on the --streaming=ext command-line option, see scpg3(1) and sftpg3(1).