SNA, VTAM and APPN Concepts & Configuration

This course is an essential requirement for all personnel working in or with an SNA network. This five-day, in-depth course introduces and explains the concepts, terminology and configuration of SNA, VTAM and APPN. Emphasis is placed upon, but is not limited to, VTAM and NCP implementations of SNA. Additionally, traditional 'subarea' SNA, APPN, and APPC are explained in detail. The course also teaches how to define the network in order to optimize response time and throughput, especially in a Parallel Sysplex. Particular attention is paid to the implementation of VTAM network definitions in order to enable support of local and cross-domains.

This course is available 'on demand' (minimum 2 students) for public presentations or for one-company, on-site presentations.


On successful completion of this course you will be able to:

  • develop an extensive SNA vocabulary
  • identify the major SNA components and their role within the architecture
  • identify and use the various address structures used in SNA
  • describe the purpose and data flow characteristics of each session type
  • explain how chaining, bracketing and pacing operate
  • identify the major SNA commands and command flows
  • characterise SNA requests and responses
  • interpret SNA message structures at each level
  • describe the operation of path control and its components
  • list the characteristics of APPC communication
  • interpret SNA data link message structures in SDLC, Token Ring, X.25, and Frame Relay networks
  • describe the importance and use of APPC verbs
  • identify the APPN node types and explain their function
  • explain the principles of APPN routing and addressing
  • define startup and session establishment procedures to VTAM
  • reinforce understanding of SNA architecture implementation
  • define network resources (major/minor nodes) to VTAM
  • avoid the most common mistakes made by new users
  • identify and code routing requirements for a VTAM network
  • code the definitions to support cross-domain communication
  • understand uses of VTAM console commands
  • describe various backup/recovery facilities
  • understand the use of VTAM generics and Multi Node Persistent sessions in a Parallel Sysplex
  • define these components in a Parallel Sysplex.

Who Should Attend

This course is ideal for all personnel working in operations, systems programming, and networking departments.


A knowledge of MVS concepts. A basic understanding of network concepts would be helpful but is not mandatory.


5 days

Fee (per attendee)

£2100 (ex VAT)

Course Code




What is SNA?; hardware and software; nodes and datalinks; SNA layers; bibliography.

Network Accessible Units

SNA NAUs; SSCP functions; CMC and data hosts; PU types and function; LU functions; NAU data flow; address awareness; network addresses message format.

SNA Sessions

Sessions and half-sessions; half session layers; session types; setup flows; initiation sequences; logon request processing; LU-LU session types.

Session Data Flow

The NAU layers; session profiles; session level pacing; adaptive session level pacing; request chaining; bracketing; Send/Receive modes; function management headers; BIND command.

SNA Message Structures

Message format and flow; RU categories; BIU structures; request header format; response header format; transmission header formats; additional TH fields; FID conversion.

Network Installation

Network planning; Network installation; MVS installation considerations; VM installation considerations; Network related data sets; VTAM start procedure; Structure of SYS1.VTAMLST; The ATCSTR00 member of SYS1.VTAMLST; The ATCCON00 member of SYS1.VTAMLST.

Network Definitions

Major & minor nodes.

Applications, Local Terminals, TRLs, Switched Major Nodes and Dynamic Models

Applications and local terminals; Application programs; Local terminals; VTAM and application programs; The Application Major Node; TSO session establishment; VTAM and Local SNA terminals; The Local SNA Major Node; VTAM and Local non-SNA terminals; The Local non-SNA Major Node; VTAM and TCP/IP; The Application Major Node for TCP/IP; TN3270; Transport Resource List for MPC + TCPIP resources; Dynamic Models; Switched Major Nodes.

Console Commands

The START command; The DISPLAY command; The VARY command; The MODIFY command; The HALT command.

User-coded Tables

Assembled Tables; Unformatted System Services (USS) logon procedure; Mode Tables; USS Tables; USSCMD macro format; USSPARM macro format; SNA/SCS message 10 example; SNA character set; Non-SNA/3270 message 10 example; 3270 commands and orders.

Path Control

Path control functions; boundary node path control; intermediate node path control; transmission groups; explicit routes; virtual routes; VR activation; route selection; virtual route pacing; FID4 TH header format; segmentation and PIU blocking.

Multi-Systems Networking Facility

MSNF terminology; Path control; Transmission groups; Explicit and virtual routes; The PATH statement; The Class of Service table (COS); Channel to Channel Adapters; Cross domain logon processing; Cross Domain Resource Managers; Dynamic CDRSC definitions; Cross Domain Resources; Adjacent SSCP Table.

Advanced Program to Program Communication

SAA: APPC and SAA; LU6.2 sessions; conversations and sessions; required information; mapped and basic conversations; APPC verbs; Generalised data stream; GDS variables. APPC Application Definitions in VTAMLST.

APPN & Enterprise Extender

Why APPN?; APPN node types; Resource registration; Resource location; LU-LU session activation; Locating resources; Route calculation; APPN Class Of Service; APPN COS definition in VTAM; APPN route setup; APPN routing; High Performance Routing; APPN/HPR and SNA; APPN/HPR message formats; ANR operation; RTP features; RTP path switching; APPN and Subarea SNA; APPN definitions in ATCSTR00; Enterprise Extender; z/OS services for SNA traffic; APPN parameters in startup options; Implementation considerations; TCP/IP implementation; IUTSAMEH; DYNAMICXCF; DYNAMICXCF & HiperSockets; Modifications to TCP/IP profile; Modifications to OSPF interface; Proof of initialisation of IUTSAMEH; VTAM implementation; Defining the XCA HPRIP major node; Defining model Major Nodes for EE connections and RTP pipes; Defining switched PUs for EE connections.

Using VTAM Generics and Multi Node Persistent Sessions in a Parallel Sysplex

Introduction to Parallel Sysplex; XCF groups; Sysplex Couple Dataset; Coupling Facility; CFRM Couple Dataset; CFRM policy; VTAM Generics ( ISTGENERIC structure); VTAM MNPS ( ISTMNPS structure).

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