Copyright: Glossary
Citation: Glossary


Microsoft SNA Server Master Table of Contents
Microsoft SNA Server

Master Table of Contents

	SNA Server Enhancements Guide
	SNA Server Installation Guide
	SNA Server Administration Guide
	Managing Microsoft SNA Server
	SNA Server Planning Guide
	SNA Server TN3270 Service
	3270/5250 Applet User's Guide
	SNA Server Reference
	SNA Server Glossary
	APPC Programmer's Guide
	CPI-C Programmer's Guide
	LUA Programmer's Guide
	SNA Device Interface Specification
	3270 Emulator Interface Specification
	Comprehensive Index


Glossary - A
Microsoft SNA Server Glossary

A B C D E F H I L M N O P Q R S T U V W X

3270

The information display system for IBM hosts (mainframes); the system includes terminals, printers, and controllers that allow a user to access host functions.

3270 LU

See LU.

3270 terminal emulation

The running of software that allows a PC to act as a 3270 terminal, displaying information from a host system (mainframe). Emulation software can also allow a PC to send print jobs from a host system to a printer connected to the PC.

5250 terminal emulation

The running of software that allows a PC to act as a 5250 terminal interacting with an AS/400 system.

802.2

The logical link control protocol used for communication over a token ring or Ethernet network. The 802.2 protocol is an IEEE standard.

A

ACTLU

SNA command sent by the SSCP to an LU to activate a session and establish session parameters.

ACTPU

SNA command sent by the SSCP to activate a PU, so that any logical units controlled by this PU are available to the SNA network.

adapter

Circuit card added to a PC to allow it to perform a specialized function, such as accessing a monitor or communications line.

address

A value that represents an individually accessible storage location. Typically, each memory location has a separate address.

Advanced Program-to-Program Communications

See APPC.

alert

A message sent to indicate an abnormal event or a failure.

allocate

(1) The process an operating system uses to respond to a request from a program to reserve memory for use by the program. (2) In APPC, a verb that assigns a session to a conversation. Contrast with deallocate.

API

Application programming interface. A programming language interface that provides information and services to application programs. APIs allow users to write their own programs for use with a specific product or in a specific environment.

APPC

Advanced Program-to-Program Communications. A method for allowing programs to communicate directly with each other, across a network or within a single system. APPC uses a type of LU called LU 6.2, and allows TPs to engage in peer-to-peer communications in an SNA environment.

APPC verb

The mechanism by which a program accesses APPC. Each verb supplies parameters to APPC. See also APPC.

AppleTalk

The network protocol used for communication with and between Macintosh computers.

application programming interface

See API.

application TP

An application program that uses APPC to accomplish tasks for end users and exchange data with other TPs in an SNA environment. For information about TPs, see the Microsoft SNA Server APPC Programmer’s Guide  and the Microsoft SNA Server CPI-C Programmer’s Guide. See also SNA Server TP and TP.

ASCII

American Standard Code for Information Interchange.

A-string

A character string composed of values taken from the Type A character set.

asynchronous communication

Communication that proceeds independently of any timing mechanism, including clock mechanisms.

asynchronous verb completion

Processing of an SNA verb where the initial API call returns immediately, so that the normal operation of the program is not blocked while processing completes. When the verb completes, the application is notified through a Windows message or event. Contrast with synchronous verb completion.

audit log

See security log.

auditing

Tracking the activities of administrators and users by recording selected types of events (for example, changing of the configuration file) in the security log of an SNA server or other Windows NT-based computer. See also security log.

automatic partnering

A setting for APPC LUs and modes that allows LU-LU pairs (with assigned modes) to be generated automatically by SNA Server. Each time a new APPC LU or mode is created with automatic partnering enabled, SNA Server searches for existing LUs and modes that also have automatic partnering enabled. SNA Server then uses all available automatic partners to create as many LU-LU pairs as possible, each pair containing a remote LU, local LU, and assigned mode. Disabling an automatic partner setting after an LU or mode has been created does not remove that LU or mode from LU-LU pairs already generated.


Glossary - B
Microsoft SNA Server Glossary

A B C D E F H I L M N O P Q R S T U V W X

backup configuration file

An extra copy of the configuration file, saved by using the File menu Backup command in SNA Server Admin. The default extension for backup configuration filenames is .SNA.

backup SNA server

An SNA server on which the configuration file is replicated by SNA Server. SNA Server will load the copy of the configuration file located on a backup SNA server if the primary SNA server goes down. One or more SNA servers can operate as backup SNA servers. Backup SNA servers are designated by using SNA Server Setup. See also primary SNA server and member SNA server.

Basic conversation

With APPC, a conversation type generally used by programs that provide services to other local programs. Basic conversations provide a greater degree of control over the transmission and handling of data. See also conversation and Mapped conversation.

Basic conversation verb

A verb used in Basic conversation. See also Basic conversation, conversation, and Mapped conversation.

basic information unit

A unit of information passed during an SNA session, consisting of an RH followed by an RU.

basic transmission unit

See BTU.

BCI

Begin Chain Indicator. In SNA, a field in the request header of the first RU of a chain, which indicates the beginning of the chain. See also chain and ECI.

bracket

A chained set of RUs and their responses, which together make up a transaction between two LUs. One bracket must be finished before another can be started.

BTU

Basic transmission unit. A standard unit of information transmitted over an SNA network. A BTU consists of the TH, the RH, and the RU. The maximum size of the BTU is controlled in VTAM by the MAXDATA= parameter and in SNA Server by the Max BTU Length parameter.


Glossary - C
Microsoft SNA Server Glossary

A B C D E F H I L M N O P Q R S T U V W X

call

To transfer program execution to another section of code and, when the called section has completed execution, allow execution to resume at the calling point.

CCITT

Comite Consultatif Internationale de Telegraphie et Telephonie. The CCITT recommends use of communications standards.

Centralized plan

An architecture for SNA networks that takes advantage of centrally-located server(s) located next to the host computer, in the same building. In the centralized plan, various LAN domains communicate with the SNA Server host environment. The host and all servers are located in one location with the entire organization tapping into these servers. All servers and clients are on the same wide area network (WAN), whether they are located in the same building or across the country, and use only one protocol, such as TCP/IP, to connect through the network. Contrast with Non-Centralized plan.

chain

In SNA, a series of separately transmitted requests treated as a single request. Used to transmit a request too large for a single request unit.

Channel

A type of SNA connection that provides direct channel attachment to a mainframe.

characteristics

See conversation characteristics.

CICS or CICS/VS

Customer Information Control System or Customer Information Control System/Virtual Storage. An interactive subsystem in which host applications can run.

click

To press and release the mouse button, thereby selecting an item. See also double-click.

client

A computer using services available through an SNA Server. While running applications such as a 3270 emulator, the client uses the SNA Server to access host or peer systems on the SNA network.

coaxial cable

A cable that consists of a conductor within another conductor, with insulation between the two conductors. The inner conductor is usually a small copper tube or wire, and the outer conductor is usually copper tubing or copper braid. It is the common medium used to connect LANs and 3270 devices. The maximum distance that a coaxial cable can be run between a 3270-type cluster controller and peripheral devices is 5,000 feet (1,500 meters).

Common Programming Interface for Communications

See CPI-C.

Common Service Verb

See CSV.

communications controller

A device that directs the transmission of data over a network (for example, the IBM 3725 front-end processor).

configuration file

A file containing setup and configuration information for SNA Server. The configuration file defines servers, connections, LUs, users, and other items. The configuration file that is loaded when SNA Server Admin starts is called COM.CFG.

connection

The data communication path between a workstation or server and other computers on the SNA network.

connectivity option

A type of connection hardware and software through which one computer communicates with other computers.

contention loser

In an APPC LU-LU session, the LU that cannot start a conversation with its partner LU (the contention winner) without first requesting permission of the partner LU. See also contention winner.

contention winner

In an APPC LU-LU session, the LU that can start a conversation with its partner LU (the contention loser). If parallel sessions between the two LUs are being used, each LU may be the contention winner for some sessions and the contention loser for other sessions. See also contention loser.

control point

A node or other SNA component that controls network resources and coordinates the activation of sessions.

control point name

A name that, when used with a network name, identifies a node or other SNA component that controls access to resources. Control point names are used in Format 3 XIDs only, not in Format 0 XIDs.

For an SNA Server connection, the Control Point Name (Remote Node) corresponds to the SSCPNAME parameter in the VTAM Start command for the remote SSCP. See also network name.

control verb

An APPC verb used to initialize or end transaction programs.

controller

A device that directs the transmission of data over a network (for example, the IBM 3725 front-end processor).

conventional Logical Unit Application programming interface

See LUA

conversation

The process used by network-based applications to communicate with each other and to exchange data in order to accomplish processing tasks.

conversation characteristics

A set of values, internal to the API, which defines the overall operation for a conversation or for a specific call. See also conversation and API.

conversation ID

A unique identifier for a conversation between two TPs.

conversation partners

Two programs involved in a conversation.

conversation security

For APPC or CPI-C, a type of security that requires a match between a user ID and password supplied by the invoking TP, and the user ID and password stored on the computer where the remote TP resides.

conversation state

A condition of the conversation that governs which call or verb can be issued by a program at a particular time. It is the conversation, rather than the program, that is in a particular state (because a program can be conducting several conversations simultaneously).

conversation verb

A verb used by TPs to allocate and deallocate conversations, send and receive data, and change conversation stages. See also TP.

CPI-C

Common Programming Interface for Communications. An SAA-adherent API that allows peer-to-peer communications among programs in an SNA environment. Through CPIC, distributed applications on computers communicating as peers can exchange data in order to accomplish a processing task, such as querying a remote data base or copying a remote file.

CPI-C calls

The mechanism by which a program accesses CPIC. Each call supplies parameters to CPIC. See also CPIC.

critical section

Part of a program that must run without interruption.

CSV

Common Service Verb. An application programming interface that provides ways of translating characters, tracing, and sending network management information to a host.

CSV verb

The mechanism by which a program accesses CSV. Each verb supplies parameters to CSV. See also CSV.


Glossary - D
Microsoft SNA Server Glossary

A B C D E F H I L M N O P Q R S T U V W X

DACTLU

An SNA command that is sent to deactivate the session between the SSCP and an LU.

DACTPU

An SNA command that is sent to deactivate the session between the SSCP and a PU.

Data link control

See DLC.

deadlock

A situation that occurs when a hung verb or call blocks the execution of other verbs or calls.

deallocate

(1) The process an operating system uses to free memory that has been previously allocated by a program. (2) In APPC, a verb that ends a conversation. Contrast with allocate.

default

The value that is automatically used if nothing is specified.

dependent local APPC LU

A local LU that allows APPC conversation with a peer system, but only via a host (mainframe) system. The type of LU used in dependent APPC is LU 6.2.

DFT

Distributed function terminal. A type of intelligent terminal supported by IBM 3270 control units, in which some of the terminal’s functions are controlled by the terminal and some by the control unit. Allows multiple sessions; connects to host systems, or to peer systems via host systems. DFT terminals are often connected using coaxial cable.

dialog box

A box used in a graphical user interface to display and solicit information.

display emulation

A feature that allows a PC to emulate an IBM 3278 or 3279 terminal. See also emulation.

display model

One of several different sizes of display:
Model 2 is 24 lines by 80 characters.
Model 3 is 32 lines by 80 characters.
Model 4 is 43 lines by 80 characters.
Model 5 is 27 lines by 132 characters.

display session

A 3270 emulation session between a network PC and a host. The session is used to emulate a 3278 or 3279 display. Also called a host display session.

display verb

An APPC verb that returns configuration information and current operating values for an SNA Server.

distributed processing

A form of information processing in which the work is performed by separate computers that are linked through a local or wide area network, using data-transfer mechanisms that enable different programs to use and share data.

DLC

Data link control. In SNA, the protocol stack layer that transmits messages across links and manages link-level flow and error recovery.

DLL

Dynamic-link library. An operating-system mechanism that automatically links executable code to an application program.

double-click

To rapidly press and release the mouse button twice, initiating an action on the selected item. See also click.

downstream connection

A connection that allows an SNA Server to support communication between hosts and clients such as IBM Communications Manager/2 systems. Even though such clients do not use the SNA Server client/server interface, with a downstream connection, they can access host connections available through an SNA Server.

downstream LU

An LU used by clients such as IBM Communications Manager/2 systems, in order to access a host connection via an SNA Server. Such clients do not use the SNA Server client/server interface, but by using a downstream LU, can receive access to connections on an SNA Server.

A downstream LU uses a downstream connection. The downstream LU is configured so that it can pass information between the client and the host.

downstream system

A client such as an IBM Communications Manager/2 system that can access host connections available on an SNA Server. Even though such clients do not use the SNA Server client/server interface, they can use a downstream connection and a downstream LU to communicate with the host via an SNA Server. The SNA Server passes the information between the downstream system and the host. With SNA Server, downstream systems appear to the host as logical units, not physical units.

duplex transmission

See full-duplex transmission.

Dynamic-link library

See DLL.


Glossary - E
Microsoft SNA Server Glossary

A B C D E F H I L M N O P Q R S T U V W X

EBCDIC

Extended Binary Coded Decimal Interchange Code.

ECI

End Chain Indicator. In SNA, an indicator in the request header of the last request of a chain, which indicates the end of the chain. See also BCI and chain.

EHLLAPI

Emulator High-Level Language Application Programming Interface. IBM’s implementation of OS/2 HLLAPI.

emulation

A process whereby one device imitates another; for example, a PC can emulate a 3278 terminal. See also display emulation.

environment variables

MS-DOS or OS/2 variables that start and stop tracing and that define the environment needed to run a particular TP.

Ethernet

A type of LAN using the 802.3 or DIX version 2.0 protocol, in which any computer can transmit at any time, but must sense for possible collisions when transmitting. On an Ethernet network, computers are linked with coaxial cable or with twisted-pair wiring.

event log

The location in which SNA Server records events involving communications hardware (for example, communications adapters) or SNA Server software. Events may include attempts to establish communication, successful establishment of sessions, failures of system components, attempts to use files that are damaged or missing, configuration problems, and responses from remote systems. Use the Windows NT Event Viewer to view event logs. See also security log.

Exchange Identification

See XID.


Glossary - F
Microsoft SNA Server Glossary

A B C D E F H I L M N O P Q R S T U V W X

file transfer

The process of sending and receiving data files to and from computers.

fill type

A value used in Basic conversations that indicates whether programs will receive data in the form of logical records or as a specified length of data.

FM profile

Function management profile. A set of parameters that govern data flow for a session on an SNA network. The FM profile is specified within the session activation request and response. FM profiles affect characteristics such as chaining, compression, headers, and brackets. See also TS profile.

Format 0 XID

A type of XID that supplies minimal information about the node. Format 0 XIDs have a fixed length. They can be used for 3270 and LUA communication, and cannot be used for APPC. See also Format 3 XID and XID.

Format 3 XID

A type of XID that supplies more detailed information about the node than a Format 0 XID. Format 3 XIDs have a variable length. They can be used for 3270 and LUA communication, and are the only type of XID that can be used for APPC. See also Format 0 XID and XID.

full-duplex transmission

Two-way electronic communication that takes place in both directions simultaneously. Also called 4-wire transmission or duplex transmission. Contrast with half-duplex transmission.

function management profile

See FM profile.


Glossary - H
Microsoft SNA Server Glossary

A B C D E F H I L M N O P Q R S T U V W X

half-duplex transmission

Two-way electronic communication that takes place in only one direction at a time. Also called 2-wire transmission. Contrast with full-duplex transmission.

HLLAPI

High-Level Language Application Programming Interface. An API that allows you to develop and run programmer-operator applications on IBM PCs (or compatibles) that communicate with IBM mainframes using 3270 emulation.

host display session

See display session.

host file-transfer parameters

In 3270 file transfers, parameters that specify the characteristics of a file being transferred (for example, the format and size of the records in the file).

host response time

The amount of time a host computer takes to reply to a message sent to it by a PC. It is measured from the moment that the PC sends the message until one of the following events: the PC receiving data back from the host, the host unlocking the PC keyboard, or the host allowing the PC to send more data.

host system

A computer system, usually a mainframe, that controls interactions between it and PCs connecting to it. A host system makes its operating system and applications available via SNA Server to PCs running software for terminal emulation or for APPC.

In SNA terminology, a host is capable of sending an ACTPU command to SNA Server, and will set up a PU-SSCP session with SNA Server.

host-addressable printer

A printer that is defined as a device associated with an LU configured as LU type 1 or 3, and that can support host printing as well as local printing.

hot backup

A configuration in which one resource (such as an SNA server) can automatically handle sessions if another cannot. SNA servers can provide hot backup for 3270, LUA or downstream sessions through pools containing LUs from multiple servers. SNA servers can provide hot backup for 5250 terminal emulation through the use of LU names that are the same on multiple servers.


Glossary - I
Microsoft SNA Server Glossary

A B C D E F H I L M N O P Q R S T U V W X

IEEE

Institute of Electrical and Electronics Engineers. An organization that maintains the standards for the 802.2 protocol used in communications on a token-ring LAN.

I-frame

Information frame. A standard unit of information transmitted over an SNA network. For 802.2 or SDLC communication, an I-frame is equivalent to a BTU. See also BTU.

implicit incoming mode

A mode that defines the properties to use when SNA Server receives a request to start a session, and the mode named in the request is not recognized by SNA Server. An implicit incoming mode allows greater flexibility in starting sessions with remote systems.

In order for a session to be established, the incoming local LU name must be recognized by SNA Server. Then the incoming remote LU must either be recognized explicitly or handled implicitly (if an implicit incoming remote LU has been configured). If the remote LU is recognized explicitly, but the mode is not recognized (as part of an LU-LU pair), SNA Server internally creates a new mode definition with the correct name, using the properties of the implicit incoming mode. Alternatively, if the remote LU is handled implicitly, SNA Server also handles the mode implicitly, by internally creating a mode, as described.

Note that an implicit incoming mode must be configured for any remote LU that will be used as an implicit incoming remote LU. An implicit incoming mode can be (but does not have to be) configured for remote LUs that will only be used explicitly.

implicit incoming remote LU

A remote APPC LU that defines the properties to use when SNA Server receives a request to start a session with a local LU, and the remote LU named in the request is not recognized by SNA Server. An implicit incoming remote LU allows greater flexibility in starting sessions with remote systems.

Note that in order for a session to be established, the local LU name must be recognized by SNA Server. If the local LU name is recognized, but the remote LU name is not recognized as a partner for the local LU, SNA Server internally creates a new remote LU definition with the correct name, using the properties of the implicit incoming remote LU.

In SNA Server Admin, before a remote APPC LU can be used as an implicit incoming remote LU, an implicit incoming mode must be configured for it.

IND$FILE

IBM’s file transfer program which allows files to be transferred from a PC to the host and vice versa. It operates in three host environments: CICS, VM/CMS, and MVS/TSO.

independent local APPC LU

A local LU that allows APPC communication with a peer system without involving a host (mainframe) system. The type of LU used in independent APPC is LU 6.2. An independent LU does not require a host system, but can work through one.

information frame

See I-frame.

invokable

Capability of a program to be started by another program. For example, an invokable APPC TP can be started in response to a request from another TP (the invoking TP).

For information about TPs, see the Microsoft SNA Server APPC Programmer’s Guide and the Microsoft SNA Server CPI-C Programmer’s Guide.

invoked program

A program that has been activated by a call or verb. See also invoking program.

invoked TP

A TP started by another (invoking) TP. The invoked TP is started by an allocate verb sent to it by the invoking TP.

For information about TPs, see the Microsoft SNA Server APPC Programmer’s Guide and the Microsoft SNA Server CPI-C Programmer’s Guide.

invoking program

A program that uses a call or verb to activate another program. See also invoked program.

invoking TP

A TP that starts another TP. The invoking TP starts the other TP by instructing the remote node to load the invokable TP.

For information about TPs, see the Microsoft SNA Server APPC Programmer’s Guide and the Microsoft SNA Server CPI-C Programmer’s Guide.

IP routed network

Internet Protocol routed network. A TCP/IP wide area network in which IP packets are propagated across the network through devices called IP routers. See also TCP/IP.

IPX/SPX

Internetwork Packet Exchange/Sequenced Packet Exchange. A set of protocols used by Novell NetWare networking software for communication across a network.


Glossary - L
Microsoft SNA Server Glossary

A B C D E F H I L M N O P Q R S T U V W X

LAN

Local area network. A high-speed communication system consisting of hardware (computers and peripherals) and software (programs and data files) that are interconnected by cable in a way that allows these resources to be shared. The connected devices are located within a limited geographic area such as a building or campus.

leased SDLC line

A dedicated telecommunications line using SDLC. See also SDLC.

link service

The software component of SNA Server that communicates with the device driver for a particular communication adapter (802.2, SDLC, X.25, DFT, Channel, or Twinax).

load balancing

Distribution of the processing load between several servers carrying out network tasks, to increase overall network performance. SNA servers can provide automatic load balancing for 3270, LUA, or downstream communications through pools containing LUs from multiple servers. SNA servers can provide automatic load balancing for 5250 terminal emulation through the use of LU names that are the same on multiple servers.

local LU

In an APPC or CPI-C conversation, the LU on the local end. Contrast with partner LU and remote LU.

local LU alias

The name by which a local LU is known to the local TP.

local node

The software component of SNA Server that interacts with clients and other nodes on the SNA network.

local printer

A printer that is attached directly to a PC.

local program

For CPI-C, the program on the local end of the conversation. See also partner program.

local TP

In an APPC or CPI-C conversation, the TP on the local end. Contrast with partner TP and remote TP. See also local LU.

For information about TPs, see the Microsoft SNA Server APPC Programmer’s Guide and the Microsoft SNA Server CPI-C Programmer’s Guide.

logical record

A unit of information that can be handled by an application.

logical unit

See LU.

Logical Unit Application

See LUA.

LU

A preset unit containing all the configuration information needed for a user, program, or downstream system to establish a session with a host or peer computer. SNA Server offers four types of LUs: 3270 LUs, used for 3270 terminal emulation; LUs of type LU 6.2, used for APPC; LUA LUs, used with programs written for the LUA interface; and downstream LUs, used to allow downstream systems to connect to a host via an SNA Server.

On an SNA Server, LUs are assigned to connections, and the connections and LUs work together to provide access to other systems on the SNA network.

LU 6.2

See LU type 6.2.

LU alias

A name that identifies an APPC or CPIC LU to TPs on the same computer. An LU alias is used only locally. See also LU name and uninterpreted LU name.

LU name

For 3270 or LUA communication, a name that identifies an LU. For independent APPC or CPIC, a name that (when used with the network name) identifies an LU to other components on the SNA network. For dependent APPC or CPIC, a name that identifies an LU to local software, such as the Windows NT Event Viewer software. See also LU alias and uninterpreted LU name.

LU pool

A number of LUs, all of the same kind, that are made available as a group. A user, LUA application, or downstream system using the pool can get LU access as long as one of the pooled LUs is available. This provides for better access for multiple users, applications, or downstream systems in an SNA installation.

LU type

Logical unit type. A subset of the SNA protocol that characterizes the communication between two LUs.

LU type 0

A protocol with minimal constraints, on which special applications can be built for SNA.

LU type 1

A protocol used by a host application communicating with a printer, sending data that conforms to the 3270 SNA Character String (SCS) definition.

LU type 2

A protocol used by a host application communicating with a 3270-type display terminal, using the SNA 3270 data stream.

LU type 3

A protocol used by a host application communicating with a printer, sending data that is 3270 data stream compatible (DSC).

LU type 6.2

A protocol used by two TPs communicating as peers. LU 6.2 works in combination with node type 2.1 to provide APPC communications using independent LUs. LU 6.2 also works with node type 2.0 to provide APPC communications with dependent LUs.

LU-LU session

A logical, two-way exchange between two LUs over a specific connection for a specific amount of time. See also PLU, session, and SLU.

LUA

Logical Unit Application. A conventional LU application, or the interface that these applications use. LUA allows workstations to communicate with host applications using LU 0, 1, 2, or 3 protocols.


Glossary - M
Microsoft SNA Server Glossary

A B C D E F H I L M N O P Q R S T U V W X

MAC

Media access control. The layer of the IEEE 802 standards that deals with network access and collision detection. In the IEEE standards, the MAC layer lies between the physical layer and the logical link control layer.

MAC address

A 12-digit hexadecimal address used by the media access control layer of an 802.2 connection. The MAC address corresponds to the VTAM MACADDR= parameter and to the Remote Network Address parameter for an 802.2 connection with SNA Server.

Mapped conversation

A conversation type generally used by programs that accomplish tasks for end users. In a Mapped conversation, the sending program sends one record at a time and the receiving program receives one record at a time. See also Basic conversation and conversation.

media access control

See MAC.

media access control address

See MAC address.

member SNA server

An SNA server that does not contain a configuration file. One or more SNA servers can operate as member servers. See also primary SNA server and backup SNA server.

mode

A collection of session properties used by LU 6.2-type LUs as they carry on a session. A mode can be used by many LU pairs at the same time.

mode name

The name used to represent a set of characteristics to be used in an APPC LU-LU session.

model

See display model.

modem

Short for modulator/demodulator. Device that enables computers to communicate over standard telephone lines by converting analog signals to digital signals and digital signals to analog signals.

modem eliminator

A device that connects two PCs through their serial communication ports, eliminating the need for a modem. Also called a crossover cable.

modem-stored phone number

A dialing method where a phone number is stored on a modem itself and dialed when needed. Contrast this with the method where SNA Server stores a phone number and sends it to the modem.

mouse

A pointing device attached to a PC; used to make choices or to position the cursor on a display.

MS-DOS

The Microsoft Disk Operating System. MS-DOS is a single-tasking, single-user operating system with a command-line interface.

MS-DOS–based client

A computer that runs the MS-DOS operating system and also uses services available through an SNA server. The client can run applications such as a 3270 emulator or APPC applications, which use SNA Server to access host or peer systems on the SNA network. See also MS-DOS.

multidrop

A connection in which one primary node communicates with multiple secondary nodes concurrently over the same physical transmission medium.

multiple sessions

Multiple concurrent sessions between an LU 6.2-type LU and multiple different partner LUs. Multiple sessions allow three or more TPs to perform operations simultaneously. See also parallel sessions.


Glossary - N
Microsoft SNA Server Glossary

A B C D E F H I L M N O P Q R S T U V W X

NCP

Network Control Program. An IBM program that supports communication controllers in single-domain, multiple-domain, and interconnected networks.

negotiable link role

A role where the SNA server negotiates with a remote system at the beginning of a session, to determine which system will control the communications. The SNA server takes a negotiable link role in connections with peer systems. See also primary link role and secondary link role.

NetView

A reporting system that runs on an IBM host (mainframe), forwarding alerts and other information back and forth between the host and PCs and other network addressable units that connect to the host.

NetView alert

A message sent to the NetView reporting system, indicating an abnormal event or a failure.

NetView user alert

A message sent by a 3270 user to a host system operator via NetView, requesting an action such as mounting a tape or changing forms on a printer. Also called user alert.

NetWare

A collection of networking software products from Novell, Inc.

network

Computer systems, controllers, terminals, and software connected in a way that allows them to communicate with each other.

network name

A name identifying an SNA network. The network name is used in combination with other identifiers, either a control point name (to identify a control point or node) or an LU name (to identify an APPC LU, particularly an independent local APPC LU). The combination of a network name with a control point name is sometimes called a network qualified control point name. The combination of a network name with an LU name is sometimes called a fully qualified network name.

node

A server, controller, workstation, printer, or other processor that implements SNA functions.

SNA defines three kinds of nodes: the host subarea node, which functions to control and manage a network; the communication controller subarea node, which routes and controls data flow through the network; and peripheral nodes, which include printers, workstations, cluster controllers, and distributed processors.

node type 2.1

An SNA component, such as an intelligent terminal or a PC, that works together with LU type 6.2 to support peer-to-peer communications, allowing the LUs to function independently from the host.

Non-Centralized plan

A common architecture for SNA Server networks based on the traditional SNA network hierarchy in which local area networks (LANs) are spread out across the business environment, connected to the mainframe computer. Contrast with Centralized plan.


Glossary - O
Microsoft SNA Server Glossary

A B C D E F H I L M N O P Q R S T U V W X

offline configuration file

An SNA configuration file that is created or modified at one site and used at another site. With the offline version of SNA Server Admin, you can create, view, or modify an offline configuration file, independent of the local running configuration. This is possible because the offline version of SNA Server Admin displays offline configurations but does not load them as the local running configuration.

operator-loaded TP

An invokable TP that is manually loaded and started by an operator.

For information about TPs, see the Microsoft SNA Server APPC Programmer’s Guide and the Microsoft SNA Server CPI-C Programmer’s Guide.


Glossary - P
Microsoft SNA Server Glossary

A B C D E F H I L M N O P Q R S T U V W X

pacing receive count

The maximum number of frames for the local LU to receive from the partner LU before the local LU sends an SNA pacing response.

pacing send count

The maximum number of frames for the local LU to send without receiving an SNA pacing response from the partner LU.

packet

A transmission unit of fixed maximum size, used as the basic unit on a packet-switching networks. A packet contains both a header and data.

packet switching

A message-delivery technique in which small units of information (packets) are relayed through stations in a computer network along the best route currently available between the source and the destination. Packet-switching networks are considered to be fast and efficient. The protocol used on packet-switching networks is X.25. See also X.25.

parallel sessions

Multiple concurrent sessions between a pair of LU 6.2-type LUs, allowing two TPs to perform multiple operations simultaneously. See also multiple sessions.

parameter

A variable used as input to a program, operating system, or API to govern how systems, programs, or functions perform.

partner LU

In an APPC or CPI-C conversation, the LU on the far end. The partner LU serves the partner TP. Contrast with local LU. See also partner TP and remote LU.

partner LU alias

A name that identifies a partner LU to partner TPs.

partner LU name

A name that identifies a partner LU to other LUs on the LU 6.2 session.

partner program

For CPI-C, the program receiving the CPI-C call.

partner program name

A name that identifies one partner program to another connected over a session.

partner program type

Indicates the type of conversation supported by the program, either Mapped or Basic. See also Basic conversation and Mapped conversation.

partner TP

In an APPC or CPI-C conversation, the TP on the far end. Contrast with local TP. See also partner LU and remote TP.

For information about TPs, see the Microsoft SNA Server APPC Programmer’s Guide and the Microsoft SNA Server CPI-C Programmer’s Guide.

path

(1) In SNA, the series of nodes and communications links over which data must travel from one LU to another. (2) A sequence of directories that identify the location of a file.

PC Support

A set of IBM programs that helps PC users access, share, and store information on an AS/400.

peer system

Mainframe, mini, or PC that communicates with another computer as an equal partner, with both computers sharing control over the communication.

peer-to-peer

A type of communication in which two systems communicate as equal partners sharing the processing and control of the exchange, as opposed to host-terminal communication in which the host does most of the processing and controls the exchange.

permanent virtual circuit

See PVC.

permissions

Settings that grant or deny a particular kind of access to a particular file, directory, or other object. For example, granting read permission but denying write permission for FILE1.EXT for Domain Admins means that members of this group can read, but not change, FILE1.EXT.

Physical Unit

See PU.

PLU

Primary logical unit. On an SNA session, the LU on the node that sent the session activation request.

pool

See LU pool.

primary link role

The role taken by the system that controls communication in an SNA session. The SNA server takes the primary link role in connections with downstream systems, and also when the SNA server is the primary station for a multidrop connection. See also negotiable link role and secondary link role.

primary logical unit

See PLU.

primary SNA server

The SNA server designated to contain the primary configuration file. There can be only one primary SNA server in the domain. The primary SNA server is designated by using SNA Server Setup. See also backup SNA server and member SNA server.

printer emulation

The ability of a PC-type printer to emulate a 3287 or 4224 printer to print host data.

printer session

A 3270 emulation session between a host and a local-area network printer connected to a PC. The printer emulates the type of printer normally used by a host system.

PU

Physical unit. A network-addressable unit that provides the services needed to use and manage a particular device, such as a communications link device. A PU is implemented with a combination of hardware, software, and microcode.

PU 2.0

In an SNA network, the component that defines controller and terminal-type resources similar to an IBM 3274 Control Unit.

PU 2.1

In an SNA network, a component such as an intelligent terminal or a PC that works together with LU type 6.2 to support peer-to-peer communications, allowing LUs to function independently from the host.

PVC

Permanent virtual circuit. A type of circuit used by an X.25 connection, where the circuit is constantly active, and the destination address is preset.


Glossary - Q
Microsoft SNA Server Glossary

A B C D E F H I L M N O P Q R S T U V W X

QLLC

Qualified logical link control. A protocol that permits SNA sessions to occur over X.25 networks.

qualified logical link control

See QLLC.

queued TP

An invokable TP that can be started by only one incoming allocate command at a time. Incoming allocate commands that arrive while the queued TP is running do not start the program again, but are queued until the program issues another RECEIVE_ALLOCATE or until it finishes execution.

For more information about TPs, see the Microsoft SNA Server APPC Programmer’s Guide and the Microsoft SNA Server CPI-C Programmer’s Guide.


Glossary - R
Microsoft SNA Server Glossary

A B C D E F H I L M N O P Q R S T U V W X

remote LU

In an APPC or CPI-C conversation, the LU on the remote end. Contrast with local LU. See also remote TP.

remote network address

For an 802.2 connection, a 12-digit hexadecimal address that identifies a remote host, peer, or downstream system. The Remote Network Address in SNA Server corresponds to the VTAM MACADDR= parameter in the PORT definition.

remote node

(1) The node at the other end of a connection. (2) The node that contains the LU at the other end of a session. (3) The node that contains the TP at the other end of a conversation.

remote node ID

One of the types of identifiers that may be used to identify a remote node. The remote node ID is an eight-digit hexadecimal number. The first three digits are called the block number, and correspond to the VTAM parameter IDBLK. The last five digits are called the node number, and correspond to the VTAM parameter IDNUM. Node IDs (local or remote) are used in both Format 0 XIDs and Format 3 XIDs. In contrast, the control point name for a remote node is used only in Format 3 XIDs. See also control point name, Format 0 XID, and Format 3 XID.

remote TP

In an APPC or CPI-C conversation, the TP on the remote end. Contrast with local TP. See also remote LU.

For information about TPs, see the Microsoft SNA Server APPC Programmer’s Guide and the Microsoft SNA Server CPI-C Programmer’s Guide.

remote X.25 address

For an X.25 connection, an address consisting of from 1 through 15 hexadecimal digits, that identifies a remote host, peer, or downstream system. When an X.25 address consists of 15 digits, the final three digits are used for routing between stations with the same 12-digit address. The Remote X.25 Address in SNA Server corresponds to the VTAM DIALNO= parameter in the PORT definition.

request unit

See RU.

Request Unit Interface

See RUI.

Response Time Monitor

See RTM.

response unit

See RU.

RTM

Response Time Monitor. A 3270 and NetView facility that monitors the amount of time it takes for a host to respond during 3270 display sessions.

RU

Request/response unit. Under SNA, a message that controls the session, data flow, and function management aspects of the SNA protocol.

RUI

Request Unit Interface. A basic interface that allows programs to acquire and release control of conventional LUs. The RUI also reads and writes request/response headers (RHs), transmission headers (THs), and request unit (RU) data. Contrast with SLI.


Glossary - S
Microsoft SNA Server Glossary

A B C D E F H I L M N O P Q R S T U V W X

SAA

Systems Application Architecture. Guidelines created by IBM to help developers standardize applications so they function in different operating environments with minimal program modification and retraining of users.

SAP address

Service access point address. A value that codes for access to certain services on an 802.2 connection within an SNA network. The Remote SAP Address parameter is used for 802.2 connections in SNA Server, and corresponds to the VTAM parameter called SAPADDR= in the PU definition.

SDLC

Synchronous Data Link Control. A type of link service used for managing synchronous data transfer over standard telephone lines (switched lines) or leased lines.

secondary link role

The role taken by the system that yields to the control of the other system during an SNA session. The SNA server takes the secondary link role in connections with host systems. See also negotiable link role and primary link role.

secondary logical unit

See SLU.

security key

An identifier used by two APPC LUs to validate security when a session is activated. The security key performs a function similar to that of a password, but at the LU-LU session level rather than at the TP-conversation level.

security log

The location in which events related to security are recorded when auditing is set up for such events. For example, auditing can be set up to create a security log entry every time the configuration file is changed on an SNA server. See also auditing and event log.

security password

The password that is required, along with the security user ID, to gain access to an invoked program when using conversation security.

security user ID

The user ID that is required, along with the security password, to gain access to an invoked program when using conversation security.

server

A PC that provides network services on a local-area network or SNA network.

service access point address

See SAP address.

service TP

A TP that uses basic conversation verbs to provide services to other TPs.

For information about TPs, see the Microsoft SNA Server APPC Programmer’s Guide and the Microsoft SNA Server CPI-C Programmer’s Guide.

session

(1) A period of time when a connection is active and communication can take place. (2) A set of resources that when activated allow communication to take place. See also LU-LU session, SSCP-LU session, and SSCP-PU session.

Session Level Interface

See SLI.

session limit

The maximum number of parallel sessions that can be active between two APPC LUs. When an LU-LU session is established, the session limit is negotiated between the two LUs.

Setup program

The SNA Server software installation program.

severity level

A number that indicates the severity of an audit or error message. Audit messages provide information and have severity 6, 8, or 10. Error messages have severity 12 or 16, indicating a problem that needs to be corrected.

side information

See side information table.

side information table

For CPI-C, a table that stores the initialization information required for two programs to communicate. The table resides in the operating system’s memory and is maintained by the system administrator by accessing a symbolic destination name. The table is derived from the configuration file for SNA Server.

single session

A limit of one session between a pair of APPC LUs, which limits the associated TPs to one operation at a time.

SLI

Session Level Interface. A higher-level interface that facilitates the opening and closing of SNA sessions with host LU 0, LU 1, LU 2, and LU 3 application programs. The SLI permits application programs to control the data traffic at a logical message level. Contrast with RUI.

SLU

Secondary logical unit. On an SNA session, the LU on the node that received the session activation request.

SNA

Systems Network Architecture. A collection of rules that brings uniformity to communications systems and the ways they interact. These rules define various functions that allow information to be transferred from one computer to another, in a form that is usable by the receiving computer.

SNA bind

The RU involved in activating an LU-LU session.

SNA Server

A Microsoft software program that allows a PC to communicate with remote computers such as IBM mainframes, AS/400s, or other PCs on an SNA network.

SNA Server PC Support router

A replacement for the IBM AS/400 PC Support program router component that enables MS-DOS–based SNA Server clients to connect to IBM AS/400 computers through an SNA server.

SSCP

System services control point. 1) A host-system network component that provides network services for dependent nodes. 2) An SNA network component that helps control and maintain communication flow between PUs and LUs on the network. Multiple SSCPs may work together in order to coordinate communications.

SSCP-LU session

A session between an SSCP and an LU; this session allows the LU to request the SSCP to set up an LU-LU session.

SSCP-PU session

A session between an SSCP and a PU. The SSCP controls the communications on the SNA network, and provides requested network services for the PU.

SVC

Switched virtual circuit A type of circuit used by an X.25 connection, where the circuit is not constantly active, but is called and cleared dynamically. The destination address is supplied when the circuit is called.

switched SDLC line

A standard telephone line used for SDLC connections on an SNA network. The line is dialed in one of three different ways: manually, by a modem that stores the phone number, or by a modem that accepts a phone number string from the software.

switched virtual circuit

See SVC.

symbolic destination name

The identifier for the side information entry. See also side information table.

Synchronous Data Link Control

See SDLC.

synchronous transmission

Transmission in which the data characters and bits are transmitted at a fixed rate, with the transmitter and receiver being synchronized. This eliminates the need for individual start and stop bits surrounding each byte. Both SDLC and X.25 use synchronous transmission.

synchronous verb completion

Processing of an SNA verb where the operation of the program is blocked until processing completes. Contrast with asynchronous verb completion.

system administrator

The person who configures, maintains the configuration of, helps users diagnose problems with, and manages a computer system. With SNA Server, this person may also be the LAN administrator.

system services control point

See SSCP.

Systems Application Architecture

See SAA.

Systems Network Architecture

See SNA.


Glossary - T
Microsoft SNA Server Glossary

A B C D E F H I L M N O P Q R S T U V W X

TCP/IP

Transmission Control Protocol/Internet Protocol. The transport protocol in use by many academic, defense, scientific, and commercial organizations to provide communication across wide area networks (WANs). TCP/IP provides communication across interconnected networks that include a variety of different operating systems (such as VMS [image], UNIX [image], and Windows NT). See also IP routed network.

terminal

A device that can send or receive data over a data communications channel. SNA Server allows for emulation of 3278 and 3279 terminals.

token ring

A type of LAN using the 802.2 protocol, in which a token is passed in a ring around the network, permitting a computer on the network to transmit data only when that computer has the token.

TN3270

A widely used protocol for encapsulating 3270 data streams in TCP sessions.

TN3270 server

A gateway for connecting TN3270 client-server data streams to standard SNA client-server data streams. Because SNA Server supports TN3270 servers, a TN3270 client (such as a UNIX workstation) can connect using the TN3270 protocol to SNA Server, which in turn connects to the host through standard SNA protocols.

TP

Transaction program. An application program that uses APPC to exchange data with another TP on a peer-to-peer basis.

For information about TPs, see the Microsoft SNA Server APPC Programmer’s Guide and the Microsoft SNA Server CPI-C Programmer’s Guide.

trace file

A file containing records of internal activities on the SNA network, including calls made to APIs, the activities of APIs, and the activities of communication links and internal flows.

tracing

The action of tracking the activities of APIs, communication links, and internal flows, including the calls made to APIs. Tracing stores a history of activity in trace files.

transaction

Data entered into a system (such as a customer deposit to a bank account), triggering a certain action (such as updating an account balance).

transaction program

See TP.

transmission service profile

See TS profile.

TS profile

Transmission service profile. A set of parameters that govern transmission during a session on an SNA network. The TS profile is specified within the session activation request and response. TS profiles affect characteristics such as pacing, sequencing, and supported requests. See also FM profile.

Twinax

Twinaxial. A connection to an AS/400 through twinaxial cable.

twisted-pair cable

Two paired wires, with each wire twisted two or more times per inch to help cancel out noise.


Glossary - U
Microsoft SNA Server Glossary

A B C D E F H I L M N O P Q R S T U V W X

uninterpreted LU name

For dependent APPC and dependent CPI-C, the name of a remote LU as defined to the remote SSCP.

user alert

A message sent by a 3270 user to a host system operator via NetView, requesting an action such as mounting a tape or changing forms on a printer.


Glossary - V
Microsoft SNA Server Glossary

A B C D E F H I L M N O P Q R S T U V W X

VCB

Verb control block. A structure made up of variables, which identifies the verb to be executed, supplies information to be used by the verb, and contains information returned by the verb when execution is complete.

verb control block

See VCB.

VINES

VIrtual NEtworking System. A collection of networking software products from Banyan [image] Systems, Inc. VINES [image] includes an addressing system called StreetTalk [image].

Virtual Telecommunications Access Method

See VTAM.

VTAM

Virtual Telecommunications Access Method. A set of IBM mainframe programs that control communications between mainframe applications and the terminals and computers that connect to the mainframe.


Glossary - W
Microsoft SNA Server Glossary

A B C D E F H I L M N O P Q R S T U V W X

WAN

Wide area network. A high-speed communication system, consisting of hardware (computers and peripherals) and software (programs and files), that provides communications services and allows resources to be shared over a larger geographic area than that served by a LAN. Contrast with LAN.


Glossary - X
Microsoft SNA Server Glossary

A B C D E F H I L M N O P Q R S T U V W X

X.25

The CCITT standard used for communication over a packet-switching network. X.25 uses the protocol called qualified logical link control (QLLC).

XID

Exchange Identification. An identifier that is exchanged between nodes on an SNA network, and that allows the nodes to recognize each other and to establish link and node characteristics for communicating. With SNA Server, there are two possible kinds of XIDs that can be exchanged: Format 0 XIDs (containing only basic information) and Format 3 XIDs (containing more detailed information). See also Format 0 XID and Format 3 XID.