VTAM Cheat Sheet

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VTAM is a complex piece of Software. But basically it's just a bit like the UNIX inetd plus network stack, allowing remote entities to access locally defined services.[1]

This article tries to help remembering things. It should serve as a quick reference for handling tasks.


Usually, configuration is stored in a partitioned data set with the partial name vtamlst. To derive it's name, look into sys1.proclib(vtam) to see the dd statements. Usually, it's

  • sys1.vtamlst, or
  • sys1.local.vtamlst.

Notable members include:

Basic configuration. The CONFIG directive designates which atccon-file to load as default.
A comma separated list of major nodes to be handled at VTAM startup.[2]

Remaining members designate major nodes. That is, textual definition files. This task is usually be done from a TSO session.

Concepts of Major and Minor Nodes

VTAM major nodes are roughly member names in the vtamlst PDS. The first non-comment line starts with a name, the literal VBUILD, TYPE=node type, and optional parameters.

Major node types:

  • ADJCP (Adjacent Control Point)
  • APPL (Application Program)
  • CA (Channel Attachment)
  • CDRSRC (Cross-Domain Resources)
  • CDRM (Cross-Domain Resource Manager)
  • XCA (External Communications Adapter)
  • LOCAL (Local SNA)
  • LUGROUP (Logical Unit Group)
  • MODEL (Model definition for dynamically created PU and LU; mostly for APPN)
  • SWNET (Switched, this is the definition of a "real" node)
  • DR (Dynamic Reconfiguration or Change)
  • ADSSJCP (Adjacent Control Point Table)
  • ADJCLUST (Adjacent cluster routing definitions)
  • APPNTOSA (APPN-to-subarea Class of Service mapping table)
  • SATOAPPN (Subarea-to-APPN Class of Service mapping table)
  • BNCOSMAP (Border node CoS mapping definitions)
  • NETSRVR (Network node server list)
  • GRPREFS (Generic resources preferences table)
  • SAMAP (Subarea mapping table)
  • SNSFILTR (Session awareness sense filter)

Administering VTAM

This is done from a system console.

VTAM is required by TCPIP, but TCPIP is smart enough to cope with VTAM being shut down and restarted without caring for TCPIP.

VTAM Start commands

VTAM is usually automatically started in the course of an IPL.

Command Comment
S NET VTAM start with defaults
S NET,,,(LIST=00) VTAM start with atcstr00

VTAM Display commands

Command Comment
D NET,APING,ID=REMNODE,LOGMODE=#INTER Create an APPC "loopback" session
D NET,APPLS Display VTAM applications status
D NET,BFRUSE Display VTAM buffers in use
D NET,CDRMS Display VTAM cross domains status
D NET,CDRSCS Display VTAM cross domain resources
D NET,COS Display VTAM cos table in use
D NET,GROUPS Display VTAM groups status
D NET,MAJNODES Display a list of active major nodes
D NET,NETSRVR Display Network Node Server List
D NET,ID=name Display VTAM resource status
D NET,ID=*.name Display VTAM resource status in any net
D NET,ID=ISTADJCP,E Display dynamic list of adjacent CPs
D NET,RTPS Display Rapid Transfer Protocol sessions. RTP is part of HPR.
D NET,TGPS Display Transmission Groups
D NET,TOPO Display APPN Topology
D NET,TRL Display Transport Resource List
D NET,U,ID=userID Display VTAM user ID status
D NET,VTAMOPTS Display VTAM startup options currently set

VTAM Vary commands

Command Comment
V NET,ACT,ID=name Activate VTAM resource
V NET,INACT,ID=name Inactivate VTAM resource
V NET,DRDS,ID=name Activate VTAM dynamic reconfiguration

VTAM Change commands

Command Comment
F NET,VTAMOPTS,startoption=option Run-Time change VTAM configuration

VTAM Halt commands

VTAM won't halt QUICK when application programs are active. Stop with the given commands.

  • TSO
Command Comment
Z NET,CANCEL VTAM abnormal termination command
Z NET,QUICK VTAM somewhat faster termination command
Z NET VTAM normal termination command


  • IBM z/OS Basic Skills Information Center: Networking on z/OS
  • IBM Redbook: P/390, R/390, S/390 Integrated Server: OS/390 New User′s Cookbook, document number SG24-4757-01


  1. Yes, this is a daring generalization. But we need to start somewhere with explanations.
  2. Major nodes can be activated manually, though.
  3. If anyone knows how to prevent the NFS-Client from starting at startup, please drop me a note.