Implementing a VTAM network

This topic explains how to implement a VTAM® network and includes the following topics:
  • Using start options and configuration lists
  • Identifying resources to VTAM
  • Verifying a VTAM network
Implementing a VTAM network involves the following tasks:
  • Use of start options and an optional configuration list
  • Identification of particular resources in the network to VTAM
  • Identification of any paths required for network routing
  • Establishment of sessions
  • Operation of VTAM itself

You will also need to understand the VTAM start procedure and the associated data sets. For information about this process, see z/OS Communications Server: New Function Summary.

This topic gives descriptions of VTAM network requirements and an example of implementing a VTAM network and includes the following subtopics:
Start options
Start options control the conditions under which VTAM runs. No matter what network configuration you are implementing, you need to code some start options. Start options are coded in files named ATCSTRxx, where xx specifies the identifier of a particular start option file.
Configuration list
A configuration list lets you specify which resources are activated automatically when you start VTAM. You are not required to define a configuration list, but it makes the VTAM operator's job easier because VTAM activates the resources in the configuration list automatically. Configuration lists are coded in files named ATCCONxx, where xx specifies the identifier of a particular configuration list.
Application programs
Each host application program you are running must be defined to VTAM as an application program minor node within an application program major node. A major node, such as an application program major node, is a set of minor nodes (in this case, the application programs) that can be activated and deactivated as a group. For more information about application programs, see Application programs.
Note: An application program may become a shadow resource if a CDRSC with the same name already exists when the major node containing the application program's definition is activated. For more information about shadow resources, see Shadow resources.
Subarea nodes
If you have one or more NCPs in your network, define them in NCP major nodes and channel-attachment major nodes.

If there are other VTAMs in your network, define connections to them in NCP major nodes, channel-attachment major nodes, or external communication adapter (XCA) major nodes. If your VTAM is to have SSCP-SSCP sessions with other VTAMs, also create a cross-domain resource manager major node and minor nodes for your VTAM and adjacent VTAMs with which your VTAM is to have such sessions.

You need to define paths for data flow between VTAM and any owned NCPs, and for data flow to and from other VTAMs and NCPs in your network over subarea connections. Paths are defined in PATH definition statements.

APPN nodes
If VTAM is going to use APPN functions, specify the NODETYPE start option.
Peripheral nodes
Other physical devices in your network must also be defined to VTAM, whether they are directly attached to the host or to an NCP. Peripheral nodes are dynamically defined or manually defined in channel-attachment, external communication adapter, local non-SNA, local SNA, LU group, model, packet, and switched major nodes. Logical units in or attached to peripheral nodes are defined with LU statements along with the peripheral nodes in the major node definitions, or if they are independent LUs, they can be defined in cross-domain resource major nodes. The major node you choose depends on the characteristics of the device you are defining.

Figure 1 is a sample VTAM subarea network. The host is running MVS™, VTAM, and two VTAM application programs. NCP11 is a channel-attached 3745 controller, and NCP12 is a link-attached 3725 controller. Peripheral nodes are connected using leased lines.

Figure 1. VTAM network
Example of a VTAM subarea network.
You need to code at least the following resources to define the network in Figure 1:
  • Start options describing the host (NETID, SSCPID, and SSCPNAME).
  • Application program minor nodes defining APPL1A and APPL1B.
  • Two NCP major nodes defining NCP11 and NCP12. These include the NCP definitions. In the NCP major node, also code GROUP, LINE, PU, and LU definition statements to define the peripheral nodes attached to the NCPs.
    Note: APPN nodes, PUs, and LUs can be defined dynamically.
  • PATH definition statements in each subarea to attach to the other subareas. For example, in NCP11, you would code two PATH definition statements to attach to subarea 1 (DESTSA=1) and subarea 12 (DESTSA=12).