Virtual-route-based transmission groups

You can also establish CP-CP sessions between two APPN-capable VTAM® nodes through a subarea network over existing subarea links and virtual routes. This is accomplished by defining a virtual-route-based transmission group (VR-based TG) between them. To define a VR-based TG, code VRTG=YES on the CDRM definition statement for the adjacent VTAM in the CDRM major nodes of both VTAMs, or code VRTG=YES as a start option at both VTAMs.

If VRTG=YES is coded at both VTAMs, then a VR-based TG is activated automatically when the CDRM session with the adjacent VTAM is activated. If there are no CP-CP sessions active between the two VTAM nodes, CP-CP establishment is automatically initiated when the VR-based TG is activated.

If CP-CP sessions are not desired over a VR-based TG, and there exists an alternate CP-CP session path between the two VTAMs, you must code VRTGCPCP=NO on the CDRM definition statement for the adjacent VTAM in the CDRM major nodes of both VTAMs, or code VRTGCPCP=NO as a start option at both VTAMs. VRTGCPCP=NO prevents CP-CP sessions from being established over the VR-based TG between the two VTAMs.

The TG number associated with a VR-TG will always be 255. In addition, a VR-TG can exist only in the following ways:

Between two interchange nodes
Between an interchange node and a migration data host
Between two migration data hosts

For more information about VR-based TGs, see the z/OS Communications Server: SNA Network Implementation Guide.

Figure 1. Virtual-route-based transmission group between interchange node and migration data host

A diagram that shows an interchange node A01N, a migration data host A17N, and an FID4 channel between the two hosts.

The following example shows virtual-route-based transmission group definitions for Figure 1.

Operand: Meaning
VRTG=YES: VR-based TG will be activated when this CDRM is established.
VRTGCPCP=YES: CP-CP sessions are supported over this VR-based TG.
CAPACITY=8K: The virtual routes comprising the transmission group have an effective capacity of 8 Kb per second.
COSTBYTE=0: The least expensive cost-per-byte-transmitted is to be associated with the transmission group.
COSTTIME=0: The least expensive cost per unit of time is to be associated with the transmission group.
NN=NO: The VR-based TG represents a connection to a migration data host.
PDELAY=TERRESTR: The maximum propagation delay of the virtual routes for the transmission group is telephone network delay (between .48 and 49.152 milliseconds).
SECURITY=UNSECURE: There is no security level for the transmission group.

**********************************************************************
* ICN#1 (A01N) definitions
**********************************************************************
         VBUILD TYPE=CDRM
*
NETA     NETWORK NETID=NETA       ** NETWORK IDENTIFIER            **
A01N     CDRM  CDRDYN=YES,        ** AUTHORIZE DYNAMIC CDRSC DEF.  **  X
               CDRSC=OPT,         ** AUTHORIZE DYNAMIC CDRSC DEF.  **  X
               ELEMENT=1,         ** HOST ELEMENT ADDRESS          **  X
               ISTATUS=ACTIVE,    ** CDRM INITIAL ACTIVATION STATUS**  X
               RECOVERY=YES,      ** CDRM AUTOMATIC RECOVERY       **  X
               SUBAREA=1,         ** NETWORK UNIQUE SUBAREA ADDRESS**  X
               VPACING=63         ** CDRM REQS BEFORE PACING RESP  **
*
A17N     CDRM  CAPACITY=8K,       ** EFFECTIVE LINK CAPACITY       **  X
               CDRDYN=YES,                                             X
               CDRSC=OPT,                                              X
               COSTBYTE=0,        ** COST PER BYTE TRANSMITTED     **  X
               COSTTIME=0,        ** COST PER UNIT OF TIME         **  X
               ELEMENT=1,                                              X
               ISTATUS=INACTIVE,                                       X
               NN=NO,             ** VR-BASED TG CONNECTS TO MDH   **  X
               PDELAY=TERRESTR,   ** TELEPHONE NETWORK DELAY       **  X
               RECOVERY=YES,                                           X
               SECURITY=UNSECURE, ** NO SECURITY LEVEL             **  X
               SUBAREA=17,                                             X
               VPACING=63,                                             X
               VRTG=YES,          ** VR-BASED TG CONNECTION REQ'D  **  X
               VRTGCPCP=YES       ** CP-CP SESSIONS OVER VRTG      **
*
**********************************************************************
* ICN#2 (A17N) definitions
**********************************************************************
         VBUILD TYPE=CDRM
*
NETA     NETWORK NETID=NETA
A17N     CDRM  CDRDYN=YES,                                             X
               CDRSC=OPT,                                              X
               ELEMENT=1,                                              X
               ISTATUS=ACTIVE,                                         X
               RECOVERY=YES,                                           X
               SUBAREA=17,                                             X
               VPACING=63
*
A01N     CDRM  CDRDYN=YES,                                             X
               CDRSC=OPT,                                              X
               ELEMENT=1,                                              X
               ISTATUS=INACTIVE,                                       X
               RECOVERY=YES,                                           X
               SUBAREA=1,                                              X
               VPACING=63,                                             X
               VRTG=YES,                                               X
               VRTGCPCP=YES
*