The environment variable SSH_SFTP_HOME_MVS determines which directory is active when the client first connects to SSH Tectia Server for IBM z/OS. By default, SSH Tectia Server for IBM z/OS uses Unix System Services home directory as the user's file transfer home directory. If the value is set to yes, the initial directory is "/_", which will make subsequent DSNs relative to the username.
The following environment variable setting (for example, in the file /home/user1/.ssh2/environment) enables user1 to use MVS side //USER1. as the default file transfer home directory: