At the local host, you can control and interrogate remote processes by using system commands prefixed with the phrase AT <hostname>. You can direct any system command to a remote host in this way. However, security restrictions can be implemented at the remote host to limit or prevent the execution of such commands.

The system provides a usercode for each system command that is directed to a remote host. If the ODT has a terminal usercode, the terminal usercode is used. You can assign a terminal usercode with the TERM (Terminal) system command. If there is no terminal usercode, the host usercode is used. You can assign a host usercode with the HU (Host Usercode) system command.

If a process uses the DCKEYIN statement to submit a system command with an AT <hostname> prefix, the system command is submitted under the usercode of the process that executed the DCKEYIN statement.

For the command to be accepted at the remote host, the associated usercode must have a USER entry and a REMOTEUSER entry in the USERDATAFILE at the remote host. Otherwise, an error occurs at the remote host and the command is not executed. The command is also rejected if no usercode is associated with it. (The command might not have a usercode if neither a terminal usercode nor a host usercode is defined.)

If the REMOTEUSER entry defines a local alias usercode, the system command becomes associated with the local alias usercode. In this case, the USERDATAFILE must include a USER entry for the local alias usercode.

The remote host inspects the USER entry of the associated usercode to find out whether SYSTEMUSER status is set for the usercode. If SYSTEMUSER status is set for the usercode, then the system command is always allowed. If the usercode is not a SYSTEMUSER, then only a limited subset of the system commands can be used.

If the command usercode does not have SYSTEMUSER status, then the output of mix display commands is filtered so that only processes running under the command usercode are displayed. Likewise, commands that specify a particular process can only be applied to processes running under the command usercode. The following are the tasking-related commands that are available: