The REXEC protocol allows an REXEC client to specify whether to use one or two connections for returning data.
For i5/OS CL command processing If you choose i5/OS® CL command processing, you can choose to use one or two connections for returning data.
For Qshell and spawned path command processing For Qshell or spawned path command processing, the REXEC server, by default returns normal output on the first connection and error output on the second connection.