Glossary

Programmatic communication based on IBM's LU 6.2 architecture. APPC provides partner programs with a common set of rules for communication.

A set of subprograms, callable from inside applications, that carry out data communications tasks.

The programmatic implementation of functions and protocols in a basic conversation between transaction programs. (See mapped conversation verbs.)

A programmatic conversation in which the applications must be able to create and interpret GDS headers (see GDS header) for transmitting and receiving data.

A remotely controlled session. See remotely controlled session.

An SNA command sent by the host to a remote LU. This command specifies the detailed protocol that the Network Service accepts before initiating an LU session.

A machine that allows multiple devices to send and receive data over the same communications link.

A front-end processor that provides an interface between the communications facilities and a computer. IBM provides programmable and non-programmable communications controllers, such as the IBM 3705, 3725, and 3745 Communication Controllers. The Intelligent Network Processor (INP) on MPE V and the Programmatic Serial Interface (PSI) on MPE XL are HP communications controllers.

A remotely controlled session. See remotely controlled session.

A locally controlled session. See locally controlled session.

Interactive commands, issued by the node manager, used to activate and deactivate APPC sessions and to monitor the activity of the APPC subsystem.

Programmatic subroutines, callable from inside applications, used to control and monitor the activity of the APPC subsystem. Control operator intrinsics implement the same functions as control operator commands. (See control operator commands.)

The logical communication between two transaction programs.

An IBM application subsystem that provides file handling and data communications services for application programs.

An LU capable of conducting only one APPC session at a time. A dependent LU always functions as a secondary LU; that is, it cannot send a BIND to initiate a session but must wait for the host to send the BIND. It can send an INIT_SELF to the host to solicit a BIND, or it can be configured to accept unsolicited BINDS. See independent LU.

The part of a network managed by a Systems Services Control Point. This includes the Physical Units (PUs), Logical Units (LUs), and links that the SSCP activates, deactivates, and otherwise manages.

The ultimate destination of data in a communications network. An end user can be a human user, a peripheral device (like a printer or a terminal), or an application program.

A locally controlled session. See locally controlled session.

See Function Management header.

A header that selects the destination or source for subsequent data transmission and supplies information for other data management tasks.

A portion of an LU 6.2 data packet that contains information about the kind of data being sent or received.

The name of the LU 6.2 data stream. LU 6.2 data packets must include GDS headers (see GDS header).

An SNA session must be supported by two sides. A half session is the resource on a Network Addressable Unit that provides FMD services, data flow control, and transmission control for its half of a complete session.

A central computer that provides services for other computers and terminals attached to it.

An LU capable of conducting multiple, simultaneous (parallel) APPC sessions with another independent LU on a remote system. An independent LU can function as either a primary or secondary LU. See dependent LU.

An SNA request to the SSCP to initiate an LU-LU session.

A trace file, created by the APPC subsystem, that records subsystem internal events and state changes.

A subprogram provided by Hewlett-Packard to perform common functions such as opening files, opening communications lines, performing subsystem-defined functions, or transmitting data over a communications line.

The TP running on the local processor.

An APPC session controlled by an LU on the local system. Also called a first speaker session. If a transaction program on the local system attempts to allocate a conversation, a locally controlled session will always be granted if one is available. If a transaction program on the remote system wants to allocate a conversation over a locally controlled session, it must ask permission of the local LU. The local LU may grant or deny the request. The APPC subsystem supports only locally controlled sessions.

A disk file, a set of disk files, or a physical device. An HP 3000 ldev is identified by a number or by a device class name.

The SNA entity through which application data is transmitted within an SNA network. Logical Units are the ports through which end users have access to the network (see end user). They format message units, display information, and handle error recovery. There can be multiple LUs in an SNA node.

An SNA LU type that defines the communication that can take place between two application programs on separate processors. LU 6.2 includes specifications for programmatic interfaces, document interchange, and data distribution.

A Logical Unit type, defined by SNA to perform a particular type of communication.

The logical connection between two logical devices in an SNA network.

The programmatic implementation of functions and protocols in a mapped conversation between transaction programs. (See basic conversation verbs.)

A programmatic conversation in which the application is freed from handling the GDS headers required by the LU 6.2 architecture.

An entity in a network that can send or receive data. The three types of NAUs are System Service Control Points (SSCPs), Physical Units (PUs), and Logical Units (LUs).

The program in the communications controller that controls data traffic for the host.

The node type for a peripheral node or cluster controller. Node Type 2.0 is supported by the APPC subsystem on MPE V and MPE XL.

The node type for a peripheral node or cluster controller capable of peer-to-peer communication. Node Type 2.1 is supported by the APPC subsystem on MPE XL.

The node type for a subarea node with a communications controller.

The node type for a host node with an SSCP (System Services Control Point).

The number of RUs that can be sent before a response is required from the receiving RU.

A device on the network, like a printer or disk drive, that functions as an end user for data.

The software and hardware of an SNA node that controls the resources of the node and reports errors and physical failures to the SSCP. There is one PU per node.

See Node Type 2.0.

See Node Type 2.1.

See Physical Unit.

The TP running on the remote processor.

An APPC session controlled by an LU on the remote system. Also called a bidder session. The APPC subsystem does not support remotely controlled sessions. See locally controlled session.

Request or response header. These are attached to SNA RUs to control data flow and support other network services.

Request or response unit.

See Synchronous Data Link Control.

A bundled HP hardware and software product that provides the logical and physical connection between the HP 3000 and an IBM host. SNA/SDLC Link/XL is used in combination with an SNA Service, such as SNA IMF, SNA NRJE, or LU 6.2 API.

See Systems Network Architecture.

System Services Control Point. An SSCP manages nodes within its domain and stores status information for personnel to maintain a network. It exists only in Type 5 nodes, implemented by the communications access method.

The data link level communications protocol used in SNA.

A comprehensive specification for distributed data processing developed by IBM. SNA defines a layered protocol for communicating and controlling a communications network within the IBM environment.

An application program that processes distributed transactions.

The portion of an SNA data packet that contains routing and sequencing information.

The programmatic implementation of functions and protocols in a conversation between transaction programs.

The SNA program on the host that controls the resources of a domain in an SNA network.