S

semaphore

A flag variable that is used to govern access to shared system resources.

server

(1) A functional unit that provides shared services to workstations over a network; for example, a file server, a print server, a mail server. (2) In a network, a data station that provides facilities to other stations; for example, a file server, a print server, a mail server.

service TP

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

session

(1) In network architecture, for the purpose of data communication between functional units, all the activities that take place during the establishment, maintenance, and release of the connection. (2) A logical connection between two network-accessible units (NAUs) that can be activated, tailored to provide various protocols, and deactivated, as requested. Each session is uniquely identified in a transmission header (TH) accompanying any transmissions exchanged during the session.

Session Level Interface (SLI)

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 Request Unit Interface.

side information table

In 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 the system administrator maintains it by accessing a symbolic destination name. The table is derived from the configuration file for SNA Server.

SnaBase

The SNA Workstation Process. It is present at all times on PCs that wish to participate in the SNA network and on PCs where dynamic loading is to be performed.

SNALink

Link support software that integrates hardware components into a SNA Server system. An SNALink is defined when a SNA Server system is installed. An SNALink can support only one physical connection from the server.

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.

subdirectory

A directory contained within another directory in a file system hierarchy.

switched virtual circuit (SVC)

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.

synchronous data link control (SDLC)

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

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 services control point (SSCP)

(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 can work together to coordinate communications.

Systems Network Architecture (SNA)

The description of the logical structure, formats, protocols, and operational sequences for transmitting information units through, and controlling the configuration and operation of, networks. The layered structure of SNA allows the ultimate origins and destinations of information, that is, the end users, to be independent of and unaffected by the specific SNA network services and facilities used for information exchange.

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.