SNA Virtual Console Communication Services System Structure
SNA Virtual Console Support provides full VM/SP console capabilities to terminal
operators on SNA terminal devices and allows the VM/SP user to use SNA termi­
nals as virtual operator consoles.
SNA Virtual Console Communications Services support the following console func­
tions: CP / CMS command processing capabilities
System product or CMS editor processing mode
Full screen support for 3270 type terminal devices
This support is provided through a virtual service machine (VSM) and the SNA
Console Communications Services (SNA CCS) in CPo The VM/VTAM Commu­
nications Network Application (VM/VCNA) program product (program number
5735-RC5) running in the virtual service machine acts as the interface between CP and the SNA network. Similarly, the SNA Console Communications Services pro­
vides the necessary interface between the existing CP system's console services and
the VM/VTAM Communications Network Application (VM/VCNA).
The screen management services are divided between the VM/VT AM Communi­
cations Network Application (VM/VCNA) and the SNA Console Communi­
cations Services (SNA CCS). VM/VCNA is responsible for the physical screen
management and therefore, the device dependent characteristics. Thus,
VM/VCNA handles such things as screen size and redisplay of the input line at the
terminal. SNA CCS is responsible for logical screen management and thus remains
relatively device independent. SNA CCS also passes the terminal input to CP and
reflects status and actions to and from the rest of the CP system.
Figure 25 on page 178 illustrates a VM/SP system with the SNA virtual console
support. The VT AM service machine (VSM) consists of an SCP, either VS 1 or DOS with External Interrupt Services (EIS), VTAM, and VM/VCNA.
SNA Virtual Console Communication Services 177
Guest
Virtual
Machine
A OP SYS or Cr1S Guest
Virtual
Machine
B OP SYS or CMS (3)
VT Ar'l Serv ice
Machine I ACF/ VM/VCNA(2) VTAM
X
(11) (10) E I OP SYS I DOS or (12)
S VS/1 I (5)1(6) I 1 I (9) (1) r---X X---- CP CONSOLE ----* SERVICES I )-* IUCV SNA CONSOLE (7) (3) (8) COMMUNICATIONS * * SERVICES (SNA CCS) I I '--------1 CP X EXISTING INTERFACE * - SNA VIRTUAL CONSOLE SUPPORT INTERFACE Figure 25. Virtual Console Support in CP
LUI
LU2 370X I -w
NCP
X
--X
X PEP 1. SNA CCS supports the SNA terminals (LUI, LU2) as virtual consoles. These
SNA terminals are attached to a 370X dedicated to the VT AM service
machine. Data entered at the terminal goes through its normal path of the NCP, CP, the SCP and VT AM. The guest virtual machine interface to CP is
the S/370 architecture provided by virtual machine simulation.
2. VM/VCNA interfaces to VT AM via the standard Application Program Inter­
face (API) in order to perform physical I/O to/from the SNA devices.
3. The terminal input is communicated to the SNA CCS via the Inter-User Com­
munication Vehicle (lUCV) SEND, RECEIVE, and REPLY protocols.
4. SNA CCS receives the interface control block (Work Element Block) with the
terminal input data. It interprets the control information that describes the
screen environment and the user's actions, and determines the action to be
reflected to CPo SNA CCS edits the input line, and passes it to CP along with
the action required.
5. SNA CCS either processes the line or sends it to the guest virtual machine for
processing.
6. Guest virtual machines request console I/O via the Start I/O interface (SIO) or via the VM/SP Diagnose X'58' facility.
178 VM/SP System Programmer's Guide
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