3270s
Planning Considerations for 3270s attachments can be considered either local or remote. Local
attachments are all devices that do not require telecommunication lines.
However, many devices that are supported for local attachment are also
supported for remote attachment. Remote attachments are devices that
are attached to binary synchronous lines. Such configurations usually
include: • a designated channel • a designated communication controller or transmission control unit • the device or control unit (for terminal attachment and/or RJE
systems) .
Remote Attachments
Both remote cluster and standalone configurations are supported. This
support includes: • Nonswitched point-to-point binary synchronous transmission. • Switched binary synchronous transmission for 3275 terminals equipped
with the Dial feature only. • Cluster configurations of up to 32 display stations and/or printers. • The local 3270 copy function. • EBCDIC (Extended Binary Coded Decimal Interchange Code) transmission
code only. • 3270s supported as virtual machine operator consoles. • CP commands allowing the operator to activate and deactivate the
teleprocessing lines, display stations and printers. • CMS Editor support. • The recording of MDR (Miscellaneous Data Recorder) records and OBR (Outboard Recording) records on the VM/370 error recording cylinder.
The MDR records are for the station and the OBR records are for the
line. The CPEREP program edits and prints these records.
The 3270 copy support allows the user to assign a screen copy
function to a 3270 program function key. pressing that key transfers
the current display image, in its entirety, to an available printer
attached to the same control unit. If the printer is busy or otherwise
not available when the copy function is invoked, the virtual machine
user receives a NOT ACCEPTED message in the screen's status area.
The following restrictions apply to V"/370's support of remote 3270s: • 3270 terminals cannot be used as primary or alternate V"/370 system
consoles.
Part 1. Planning for System Generation 51

3270s • The number of binary synchronous lines supported by VM/370 for 3270 use is 16 minus the number of 3704/3705 Communications Controllers in NCP mode minus one (if there are any 3704/3705 Communication
Controllers in EP mode). • The CP DIAL command is not supported. 3270 Support on Binary Synchronous Lines
The supported display devices on binary synchronous lines have the same
flexibility and usefulness as locally attached 3270 devices, except for
the following limitations: • lnguiry Retrieval Speeg -- Because the 3270 remote stations are subject to (1) relatively slow teleprocessing
transmission speeds and (2) the mechanics of polling screen display and data entry are not as rapid for remote 3270 devices as they are for locally attached 3270s. • CP DIAL -- The CP DIAL and ATTACH commands are
not supported for remote 3270 stations. • Hard £2£I of 1270 -- Just as users of locally attached 32 7 0 display devices can spool their virtual console input and output
to the system printer, so can the users of remote 3270 display
devices. However, for remote 3270 users, and those local 3270 users
whose terminals may be physically distant from the system printer, provides a limited hard-copy facility at the local and remote
locations. • IES! and IEST Eeys -- These keys on the 3270 terminal
are not supported for remote 3270s. The Test Request function on
locally-attached 3277s is supported by the TEST REQUEST key; it is
supported on locally-attached 3278s by the SYSTEM TEST key.
Remote Hardware Configurations Supported VM/370'S support of remote 3270s requires: • a binary synchronous line • a transmission control unit • terminal devices (display stations and/or printers)
and associated control units
The binary synchronous line must be in 2701/2703 mode. The
transmission control units supporting remote 3270s on binary synchronous
lines are: • Integrated Communications Adapter (ICA). • IBM 2701 Data Adapter Unit with Synchronous Data Adapter Type II. • 2703 Transmission Control with Synchronous Data Adapter Type II. • IBM 3704 and 3105 Communications Controllers in emulation mode. A 3704/3705 line is in emulation mode when it is controlled by the
Emulation Program (EP). 52 IBM VM/370 Planning and System Generation Guide