Page of GC20-1821-3 As Updated April 1, 1981 by TNL GN25-0840 To connect a terminal supported by both VM/370 and a multiple-access
system, use the CP DIAL command. Such terminals can be on either
non-switched or switched lines. To connect a terminal to the virtual
machine defined in Figure 8, enter this command:
dial vm370 The VM/370 system matches the terminal type to an equivalent virtual
line that is available and enabled (in this example, 070, 080, 081, 082, or 083). Once a connection is made, the virtual machine controls the
terminal to which it is logically connected (in this example, the VM/370 virtual machine). It remains connected until logoff using standard
logoff procedures or until the virtual ,machine is forcibly logged off. Once logged off, the user is then free either to log onto VM/370 or to
use the DIAL command to contact another multiple-access system.
Dial-up terminals supported by a multiple-access system may be of a
different type than those supported by VM/370 as virtual system
consoles. Such terminals must be on switched lines, and the CP DIAL
command cannot be used. Users must dial the multiple-access system's
telephone numbers directly.
As shown in Figure 9, a communications system can be tested by using
multiple virtual machines in place of multiple real machines. For
example: While there exists a single two-line 2701 on the real machine,
the virtual 2701 units could each be defined as a one-line 2701. System/370 VM1 VM2 r--------, I I I I I I , VM/370 virtual 2701 Virtual 2701 L- ____________________ I I I Real 2701 I L--, I I r------, IData I <------------------------------->IDatal I set I Communications Line I Set I , .J I , Note: This fiqure assumes that the real 2701 transmission control unit Is-equipped with the appropriate data sets and line capability.
Figure 9. A Communications Test System Section 1. General Considerations 29

April 1, 1981 FiguLe 10 illustrates a virtual transmission control unit running
remote 3270 units. When the terminals supported by the multiple-access system are not
those supported by as virtual operator consoles, the 'real line
appearances must be one of the following: • Defined in the VM/370 directory entry for the virtual machine via the
DEDICATE control statement; for example:
DEDICATE vaddr raddr
where: vaddr is the virtual address, and raddr is the real address of the--appropriate line appearance-on--the real transmission
control unit.
or -- • Attached to the virtual machine by an operator with privilege class
B; for example:
attach raddr to vml as vaddr
where: is the real address of the appropriate line appearance
on the real transmission control unit, and is the
address of the line appearance as generated in the virtual
machine operating system. .-- I I I I I , 1 I 1 I I I L- System/370 VM1 .----- I I I I '--- VM/370 Virtual 2703 ________________________________________---J Datal Set I Real 2703 communications Line '----------------------" , IData I Set '----_J 1 ----,
Data I Set I "'--- ___ ,J _...;.r-, ---. __ r"1 ------... ___ 13275 ___ I 3275 I J L- ___ J Figure 10. A Virtual 2703 TCU Controlling Remote 3270 Terminals 30 IBM VM/370 Operating Systems in a Virtual Machine