Terminal emulators

z/OS provides several terminal emulators that you can use to access the shells:

The TSO/E OMVS command, a 3270 terminal interface
The rlogin command, an asynchronous terminal interface
The telnet command, an asynchronous terminal interface

When selecting a terminal emulator, there are several key points to consider:

Code page conversion: By default, z/OS UNIX System Services operates in the POSIX locale (also known as the C locale) using code page IBM-1047, but it can operate in other locales, including double-byte locales. Unless you change the locale in the shell so that the code page used by the shell matches the code page used by the workstation for the z/OS UNIX session, a terminal emulator must perform some code page conversion. Mechanisms are provided to specify the conversion required for your situation:
- The OMVS command has the CONVERT parameter to specify the conversion between the code page used at your workstation and the code page used in the shell.
- rlogin and telnet convert from ASCII ISO8859-1 to EBCDIC IBM-1047 by default. Once you are logged in to the shell, you can use the chcp to select other code pages to convert between for the session.
Number of sessions: Some terminal emulators allow multiple interactive sessions for the same user. This can be accomplished by multiple logins or by using an emulator that allows multiple sessions with one login.
File editing: With the OMVS emulator, you can use the ISPF editor. For the other terminal emulators, vi is the editor of choice.
Shell mode: rlogin and telnet provide both line mode (also known as canonical mode) and raw mode, while OMVS operates in line mode only. Line mode is sufficient for most shell utilities. However, the full function of certain useful utilities, such as vi and the command line editing feature of the shell, are available only in raw mode.
When you first login to the shell, you are in line mode. Depending on your means of access, you may then be able to use utilities that require raw mode or run an X-Window application.
line mode

Your input is processed after you press <Enter>.

raw mode

Each character is processed as you type it.

graphical mode

A graphical user interface for X-Window applications

Figure 1. The OMVS interface to the shell

With the OMVS interface, there is one login for an ID with multiple sessions, only line mode can be used, you can switch to TSO/E from the shell, and use ISPF shell to perform z/OS UNIX tasks. You can use the ISPF, ed, or sed editors. DBCS support is available.

Figure 2. The asynchronous terminal interface to the shell

In the asynchronous terminal interface to the shell, there can be multiple logins for an ID, with one session for each login. Line mode and raw mode is available. Use the chcp shell command to set the code pages. You cannot switch to TSO/E from the shell but you can run TSO/E commands from the shell. You cannot use the ISPF shell. You can use the vi, ed, or sed editors. DBCS support is available.